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Dissertations and Theses Dissertations and Theses

2-10-1986

Biostratigraphy of the Cowlitz Formation in the Biostratigraphy of the Cowlitz Formation in the

Upper Nehalem River Basin, Northwest Oregon Upper Nehalem River Basin, Northwest Oregon

Neil B. Shaw Portland State University

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Recommended Citation Recommended Citation Shaw, Neil B., "Biostratigraphy of the Cowlitz Formation in the Upper Nehalem River Basin, Northwest Oregon" (1986). Dissertations and Theses. Paper 3654. https://doi.org/10.15760/etd.5538

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'

"

AN ABSTRACT OF THE THESIS OF Neil B. Shaw for the Master

of Science in Geology presented February 10, 1986.

Title:Biostratigraphy of the Cowlitz Formation in the

upper Nehalem River Basin, northwest Oregon

APPROVED BY MEMBERS OF THE THESIS COMMITTEE:

Ric::J,~ Thoms~~ Ch~:=~:

Robert Van Atta

Examination of stream and roadcut exposures of the

Cowlitz Formation allows the selection of measured repre-

sentative sections, and collection of fossils, from an area

roughly defined by the intersection of the boundaries of

Clatsop, Columbia, Tillamook and Washington counties in

Oregon. The study defines the features of the local

environment of deposition, correlates sections to derive a

composite columnar section, and develops a checklist of

species for both microfossils and megafossils of the Cowlitz

Formation.

A composite columnar section of 720 m, based on

three stream sections and one roadcut section is

2

presented. Twenty-two selected samples yielded fossil

assemblages which included a total of forty~seven species

of foraminifera, twenty-seven species of macrofossils and

a small number of terrestrial plant fossils and trace fossils.

Paleoecologically diagnostic species and assem­

blages indicate that the features of the environment of

deposition varied. Water depth varied from upper

bathyal or outer neritic in the lower Cowlitz Formation, to

possibly inner neritic during deposition of the upper

Cowlitz sands. Cool bottom temperatures and probably

warm, stratified surface waters are also indicated.

The integration of paleontological and sedimentary

structural evidence has resulted in (number) models

proposed for the environment of deposition of the Cowlitz

Formation. A comparison of these models is made.

The composite section is assigned to the Narizian

foraminiferal Stage of Mallory. Only one zone, the Plecto­

frondicularia P. ~nkinsi Zone of Rau is recognized. It is

represented by two faunules, the Plectofrondicularia -

Lenticulina (lower) faunule, and the Cibides - Lenticulina

(upper) faunule. A narrow overlap of the teilzones of

Cyclammina pacif ica Beck and Lenticulina texanus

(Cushman and Applin) permits local correlation.

One measured section, the Sunset ·Camp Section, was

continued across the Cowlitz-Keasey contact in order to

achieve stratigraphic control. The Narizian-Refugian

"

3

stage boundary appears to be coincident with this contact

in this section. The fossils recovered from the Keasey

Formation above the Cowlitz-Keasey contact were

assigned to the Sigmorphina schenki Zone of Rau. This

contact is gradational and poorly defined. A marked

reduction in mica characterizes Keasey rocks as well as

the disappearance of the foraminiferal species Cibicides

natlandi Beck, the occurrence of which is considered here

to be diagnostic for the Cowlitz Formation.

The Cowlitz Formation in the study area can be

correlated with the type Cowlitz Formation in southwest

Washington, the Spencer Formation, Yamhill, the Nestucca

and the Coaledo Formations of Oregon, the Mcintosh

Formation of Washington and the Tejon Formation of

California.

BIOSTRATIGRAPHY OF THE COWLITZ FORMATION IN

THE UPPER NEHALEM RIVER BASIN, NORTHWEST OREGON

by

NEIL B. SHAW

A thesis submitted in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE in

GEOLOGY

Portland State University 1986

ii THE OFFICE OF GRADUATE STUDIES AND RESEARCH:

The members of the Committee approve the thesis of

Neil B. Shaw presented February 10, 1986

.. R· ichard Thoms. ---

- Leonard Palmer

Robert Van Atta

Approved:

Paul Hammond, Head, Department of Geology

Dean of Graduate Studies and Research

iii

ACKNOWLEDGEMENTS

The author was aided in his work on this project by

a number of persons and several institutions, all of whom

cannot be named here. Those who come to mind most

prominently are: Dr. Richard Thoms who suggested this

project and whose company I enjoyed both in the field

and in the laboratory; my wife Maureen who assisted me

in the field and whose savings helped me to complete

graduate school; and my parents who provided me with a

pickup truck for my field work and who opened their

kitchen to me for messy disaggregation work. I thank

AMOCO Exploration Company and DOGAMI for lending

financial support. Longview Fibre Company foresters in

Vernonia generously provided me with air photos, direc­

tions, and permission to access their land. Dr. David

Taylor provided much appreciated advice. Gina Luckey

did a good job of typing this paper. Many thanks to Bob

Johnson who gave me summer-long permission to camp

on his property near Keasey.

TABLE OF CONTENTS

ACKNOWLEDGEMENTS

LIST OF FIGURES

LIST OF PLATES

CHAPTER

I INTRODUCTION

II GEOLOGY

Introduction

Tillamook Volcanics

Columbia County Quarry

S & P Railroad Cut

Cowlitz Formation

Nehalem River Section

Rock Creek Section

New Road Slump Section

Sunset Camp Section

Keasey Formation

III PALEONTOLOGY

Foraminifera

Other Fossils

IV PALEOECOLOGY

Introduction

iv

PAGE

iii

vi

vii

10

10

14

16

17

18

22

31

38

48

55

58

58

58

64

65

I

v

v

Plectofrondicularia - Lenticulina Faunule 65

Cibicides - Lenticulina Faunule

Environment of Deposition of the

Upper Sand Member

AGE AND CORRELATION

66

67

79

Local Biostratigraphy 79

The Narizian-Refugian Stag~ Boundary 80

SYSTEMATIC CATALOGUE 82

DESCRIPTION OF LOCALITIES

BIBLIOGRAPHY

94

101

~,

FIGURE

1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

LIST OF FIGURES

Thesis Areas of Previous Workers

Thesis Area

Correlation Chart

Geologic Map of Thesis Area

Nehalem River Section

Nehalem River Columnar Section

Nehalem River Cross Section

Rock Creek Section

Rock Creek Columnar Section

Rock Creek Cross Section

New Road Slump Section

New Road Slump Cross Section

Sunset Camp Section

Sunset Camp Columnar Section

Sunset Camp Cross Section

Correlation of Sections

Checklist of Species

Deep Channel (Bruer) Model

Delta Face Model

Inner Neritic Model

Chan of Dott/Myers Model

Upper Bathyal Model

Bathymetric Curve

vi

PAGE

3

5

11

12

23

24

25

32

33

34

39

40

49

50

51

57

59

69

69

70

72

76

78

vii

LIST OF PLATES

PLATE PAGE

1. Columbia County Quarry 15

2. Columbia County Quarry 15

3. S and P Railroad Cut 17

4. Upper Cowlitz Sand 41

5. Soft Sediment Deformation 42

6. Leisegang Banding 43

7. Landsliding and Small Scale faulting 43

8. Clay Parting 44

9. Unconsolidated "Clark and Wilson" Sand 45

10. "Chippy" Upper Mudstone 46

11. New Road Slump 47

12. New Road Slump 47

CHAPTER I

INTRODUCTION

The northernmost portion of the Oregon Coast Range

is characterized by an up-arched volcanic core, which has

been named the Tillamook Volcanics Series (Snavely and

Others, 1968). On the northeastern flanks of this vol­

canic high lies a series of marine sedimentary formations

of Upper Eocene to Middle Miocene age. The oldest of

these superjacent sedimentary formations is the Cowlitz

Formation.

Although the Cowlitz Formation in Oregon was

studied by such early workers as Diller (1896), who

mapped the sedimentary units exposed in the bed of Rock

Creek near Vernonia, comprehensive mapping and

paleontological work did not take place until 1945 with

the work of Warren and Norbisrath. Their map of

northwestern Oregon remains the standard to which all

subsequent work has been compared. Van Atta (1971),

Jackson (1983) and Timmons (1981) subsequently

mapped the area in more detail, but modifications of the

1945 map have been minor.

The discovery of natural gas in the Cowlitz Formation

near Mist, Oregon in 1979 spurred further interest in the

2

presented. Twenty-two selected samples yielded fossil

assemblages which included a total of forty-seven species

of foraminifera, twenty-seven species of macrofossils and

a small number of terrestrial plant fossils and trace fossils.

Paleoecologically diagnostic species and assem-

blages indicate that the features of the environment of

deposition varied. Water depth varied from upper

bathyal or outer neritic in the lower Cowlitz Formation, to

possibly inner neritic during deposition of the upper

Cowlitz sands. Cool bottom temperatures and probably

warm, stratified surface waters are also indicated.

The integration of paleontological and sedimentary

structural evidence has resulted in several models

proposed for the environment of deposition of the Cowlitz

Formation. A comparison of these models is made.

The composite section is assigned to the Narizian

foraminiferal Stage of Mallory. Only one zone, the Plecto-

frondicularia P. jenkinsi Zone of Rau is recognized. It is

represented by two faunules, the Plectofrondicularia -

Lenticulina (lower) faunule, and the Cibides - Lenticulina

(upper) faunule. A narrow overlap of the teilzones of

Cyclamrnina pacif ica Beck and Lenticulina texanus

{Cushman and Applin) permits local correlation.

One measured section, the Sunset Camp Section, was

continued across the Cowlitz-Keasey contact in order to

achieve stratigraphic control. The Narizian-Refugian

3

OBLINSKI -NELSON

;\;

FIG.1 THE COWLITZ FORMATION AS IT OUTCROPS IN THE THESIS AREAS OF JACKSON, NELSON, OBLINSKI, AND TI~r10NS.

4

recently studied by Timmons (1981) and Jackson (1983).

The reason for limiting the study area as much as possible

was that sections found close by one another geo­

graphically were apt to be more closely related litho­

logically and paleontologically, and therefore could

produce a more rational composite section.

Figure 2 shows the several measured sections and

collection sites of this project within the field area.

This area is located almost entirely in the westernmost

portions of Washington and Columbia Counties in Oregon.

The field area is conveniently close (50 km) to

Portland via U.S. Highway 26 (fig. 2). It is also gen­

erally well provided with good all-weather roads. Many

of these are maintained by logging companies such as

Crown Zellerbach Corporation and Longview Fibre

Company. However, access is limited in some areas to

those who secure permission from the companies

involved. Macadamized county roads serve an area that

has been important as a timber harvesting area since

before the turn of the century. Landowners generally

allow access to their private roads and riverside

property. Rugged vehicles are recommended for all off­

highway travel.

The upper Nehalem River Valley is oriented north-

south in the field area (fig. 2). This is controlled by the

occurrence of erosionally resistant volcanic rocks of the

FIG.2

THESIS AREA

0 I 2

m

U S. H I

~ s.e ,f;!:;:d CUt~•h•l•m ------ "'1;.,,,.,,,

~·-----, ____ _ -. I

New Road Slump SectlOll

Rocky Point

Col.JmbiB

~~·

." '

I I

I

5

6

Tillamook Volcanics to the west. The Nehalem River and

its tributaries erode the less resistent Tertiary sediments

which lie to the east and exhibit the meander patterns

characteristic of low-gradient stream flow. Fault­

controlled "diamond" drainage patterns characterize the

indurated volcanic conglomerates exposed to the west of

Timber. Dendritic patterns predominate in the volcanic

highlands.

The thesis area is very heavily forested. Bedrock

exposures are limited to the beds of streams and to fresh

roadcuts and railroad cuts. High rainfall and humid

conditions throughout most of the year cause rapid

weathering and destruction of outcrops. Some formations

such as the Keasey are particularly vulnerable to rapid

weathering and subsequent landsliding.

Field Work

The field work for this project was completed during

the summer and fall of 1984. Stream traverses yielded

the best exposures of the Cowlitz Formation as well as

superjacent and subjacent formations. In selecting

appropriate sections, most of the tributaries of the

Nehalem River in the field area were traversed. These

included Rock Creek, Fall Creek, Wolf Creek, Louisinont

Creek and the Nehalem River itself. Most of the possible

sections examined could not be used for a variety of

7

reasons including lack of stratigraphic control, extreme

faulting, and/or excessive stream bedload cover.

Measurement of stream sections was made with the

use of a 50 meter tape. Samples were taken from the

stream bottom as required by the stratigraphy and at

twenty-meter intervals within the more massive units.

Bedding plane attitudes were taken with the use of a

Brunton compass and a "dip stick." The "dip stick" was

simply a three-foot length of one-and-one-half inch

diameter dowel with small squares of plywood screwed to

its ends at perfect right angles. This simple device made

it possible to measure submerged bedding plane surfaces.

When the lower plywood square was placed on a

submerged bedding plane, the attitude of the upper,

parallel plywood plane above the water level could be

measured conveniently •

Road cuts offered many exposures of the Cowlitz and

Keasey formations as well as the Tillamook Volcanics,

particularly in the Rocky Point area where logging roads

often yielded fresh exposures. However, road cuts were

generally regarded with suspicion because of frequent

landsliding and creep on the often steep, wet slopes of the

highlands. One excellent, nearly continuous exposure of

the upper Cowlitz Formation, including its contact with the

superjacent Keasey Formation, was included here. Found

near Rocky Point, and named the "New Road Slump"

Section, it offered nearly vertical exposures of sedi­

mentary structures in the Cowlitz Formation.

Maps used in field investigations included the USGS

Clear Creek (1955) and Timber (1955) 7.5 minute quads.

Also, recent (1984) aerial photographs at a scale of

approximately 1:12000 were used for investigations in

areas where logging roads had been very recently

constructed.

Laboratory Work

One hundred-sixty-one samples were selected from

8

three measured sections for disaggregation. Splits of all

samples which yielded Foraminifera were isolated for

storage at Portland State University. In addition to these

samples which were taken to isolate Foraminifera, a

number of samples containing mollusks, plant leaf and

stem impressions, and some trace-fossils were collected.

These fossils were isolated from their rock matrices and

all poorly preserved specimens discarded. Well preserved

specimens were given PSU location numbers, named, and

deposited in the Portland State University Earth Sciences

Museum.

Fine-grained rocks suspected of containing

Foraminifera were disaggregated using the kerosene­

boiling water technique. Calcite-cemented rocks

unaffected by this treatment were discarded. Eighty-two

9

samples produced microfossils. Of these, twenty-two were

selected as samples which contained representative

species assemblages within critical stratigraphic intervals.

Sampling sites were given Portland State University

location numbers. Hypotype slides and assemblage slides

of Foraminifera were prepared and deposited in the

Portland State University Earth Sciences Museum.

CHAPTER II

GEOLOGY

Introduction

The Cowlitz Formation, a thick sequence of mostly

continentally derived, micaceous, arkosic sediments of

Eocene age is exposed in the Keasey-Timber-Cochran area

on the eastern flank of the Tillamook Highlands of the

northern Oregon Coast Range. Partial exposures of the

Cowlitz Formation along the tributaries of the upper

Nehalem River yield a composite stratigraphic thickness of

720 m. The Cowlitz is typically found at lower elevations;

the highlands to the west are largely occupied by the

basalts and volcaniclastics of the Tillamook Volcanics

which underlie the Cowlitz. Easterly, the Cowlitz

Formation is overlain by the tuffaceous, poorly-micaceous

mudstones of the Keasey Formation.

The Coast Range Province of northern Oregon is

characterized by a series of marine sediments and

volcanic rocks which have been folded into a broad

anticlinorium. This structure plunges to the north of the

Tillamook Highlands. The central portion of the

anticlinorium is occupied by the volcanic flows, breccias

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FIG.4

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................ ................ ................ ................ ................ ................ ................ ................ ................ ................ ................ ................ ................ .. . . . ... ... .. . .. ················ ................ 0 5 "'

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PITTSBURG BLUFF

KEASEY

COWLITZ

TILLAMOOK VOLCANICS

12

13

and sediments of the Tillamook Volcanics. Draped around

the nose of the structure to the north is a sequence of

younger Tertiary sedimentary formations called the

Nehalem Group by Van Atta (1971). From oldest to

youngest this group includes the Cowlitz Formation of late

Eocene age, the Keasey Formation of Late Eocene to early

Oligocene age, the Pittsburg Bluff Formation of middle

Oligocene age, and the Scappoose Formation of middle

Miocene age (fig. 3). The Scappoose Formation inter­

fingers with and is capped by flows of Columbia River

Basalt deposited during middle Miocene time.

The Cowlitz Formation in the Nehalem River basin

outcrops in a discontinuous arc surrounding the highlands

of Rocky Point (fig. 1). This outcrop configuration in map

view does not indicate the true lateral extent of the

formation, which is somewhat greater when subsurface

occurrences are included. The Cowlitz Formation is

thickest in subsurface several kilometers to the north of

the field area near Mist (Bruer, 1984).

This study is based on four measured secti6ns and

two sample sites. These were selected to provide a

composite columnar section of the Cowlitz Formation

including its contacts with the Tillamook Volcanics and the

Keasey Formation. These sections were then positioned

relative to one another based on an observed species

range overlap of two Cowlitz Formation Foraminifera.

14

These two species were Cyclammina pacifica Beck, which

was found in the lower part of the Cowlitz and the other

Lenticulina texanus (Cushman and Applin) which was

found in sections which included the upper Cowlitz.

Tillamook Volcanics

The Tillamook Volcanics (Snavely and others, 1968)

is an accumulation of Eocene basaltic flow rock, minor

pyroclastics, breccias, mudflows, conglomerates, tuffs,

and minor volcanic sediments which represent the

products of alkali-basaltic volcanism. It has been

concluded by Jackson (1984) that the Tillamook Volcanics

rocks are similar to oceanic volcanic piles such as the

Galapagos Islands and Iceland. In fresh hand sample the

basalts and basaltic andesites of the Tillamook Volcanics

Series are typically medium grey, aphanitic to somewhat

porphyritic, often exhibiting large plagioclase crystals.

Flow rocks tend to weather to a dark orange "rust" color.

In this report, strata of the Tillamook Volcanics are

found in depositional contact with the overlying Cowlitz

Formation in the Nehalem River Section, the S and P

Railroad Cut, and in fault contact with the Cowlitz in the

Rock Creek Section. The basalts of the Columbia County

Quarry, also referred to in this report, may represent a

slide block of Tillamook Volcanics rock which came from

16

Rocky Point, a local high of Tillamook Volcanics flow rock

immediately to the west of the quarry (Timmons, 1981, p.

3 5) •

Cowlitz-contemporary volcanic rocks have been

referred to as the Goble Volcanics (fig. 3). Goble

Volcanics rocks are so similar to Tillamook Volcanics

rocks that differentiating between them is very diff i­

cult, even with the use of trace-element (INAA)

geochemical techniques (Jackson, 1984).

A small quarry near Rocky Point (fig. 1) (plate 1)

exposes two layers of basalt which may be either Goble

Volcanics or Tillamook Volcanics (plate 1). Between the

two layers there is a discontinuous boulder to pebble

conglomerate of variable thickness (top of outcrop, plate

1). The conglomerate and associated sediments have a

distinctly reddish color (plate 2). The conglomerate

layer, as well as a rubbly zone on the northwestern rim of

the quarry offers a variety of fossils of inner neritic and

littoral zone animals such as Ostrea, Volsella, Mytilus,

and Terebratalia.

This quarry has been examined by many geologists.

and paleontologists. Van Atta (1971), Nelson (1977), and

others have interpreted this outcrop (plate 2) to repre­

sent an intrusion of Goble basalt into mudstone and

conglomerate, the conglomerate between the basalt

17

layers representing a "sliver of intrusion-displaced host

rock" (Timmons J.981, p. 19).

Timmons finds that the ha salt layers r(~present

subaqueous or subaerial flows, probably in .a littoral zone.

Sulf Lde mineralization in the conglomerate and sedi­

mentary layer; angular, apparently autobrecciated rubble;

and the presence of red, higher oxidation state (ferric)

iron oxide; all suggest a subaerial or submarine flow, as

opposed Lo an intrusion.

A large, (up to 30 m) nearly vertical bank along the S

& P Railroad track near Cochran (plate 4) offers an

excellent exposure of Upper Eocene sedimentary material

wl1ich contains many fossils of stems and le~ves of trees

and other plants.

pl.3

18

Jackson (1983), mapped this outcrop as part of the

Tillamook Volcanics Series. This author, however, is

inclined to group this outcrop with the conglomeratic basal

member of the Cowlitz Formation, using Warren and

Norbisrath's definition of local conglomerates in the

Cochran area.

The lowermost portion of this outcrop is composed of

a dark, greenish-grey, very poorly sorted volcanic sand

with included boulders. This volcanic sand and boulder

assortment is sharply defined at its uppermost limit by a

distinct plane, forming an indurated shelf in places.

Overlying this is a poorly sorted conglomerate containing

rounder cobbles and boulders interstratified with light

tan, tuffaceous, bedded siltstone. The siltstone beds yield

the numerous plant fossils mentioned above.

Plant forms in the S and P Railroad Cut include the

abundant reed Last_~a, the common sycamore-like tree

Planatophyllum, abundant scouring rush Equisetum (the

Eocene forms were much larger than those found in the

Coast Range today), and the cypress Chamaecyperus

(Cameron, 1977).

Cowlitz Formation

The Cowlitz Formation in the Nehalem River Basin can

be divided (Warren & Norbisrath, 1946) into four informal

members based on lithology: a basal conglomerate, a

lower mudstone, a sandstone, and an upper mudstone which

19

grades into the overlying Keasey formation. The Cowlitz

in the study area is characterized by an abundance of mica

even in very fine-grained samples. This aids in distin­

guishing it from the overlying basal Keasey formation

which is mica-poor. In the field, this is frequently the

only feature which can be used to locate the Cowlitz­

Keasey contact. (Van Atta, 1984)

The name Cowlitz, as used to designate the upper

Eocene sediments in the upper Nehalem River basin, was a

problem almost as soon as it was first used by Warren and

Norbisrath in 1946. Deacon (1954) formally called this

name into question by noting lithological differences

between the typical Cowlitz Formation. in Washington and

those strata which interfinger with volcanic rocks in Rock

Creek in the study area. He proposed, alternatively, the

name Rocky Point Formation (Rocky Point appears in the

center of a ring of Cowlitz Formation outcrops in the

Neha~.em River basin). Niem (oral comm. 1984) also called

the name into question, citing paleontological differences,

most notably the presence of the deep-water form

Plectofrondicularia packardi Beck in the Nehalem River

Basin, and its complete absence in the type-Cowlitz

sediments of Washington. Van Atta (1971), however, in

his study of the Tertiary formations in the upper Nehalem

River Basin favorably compared type-Cowlitz Formation

strata with those in Northwest Oregon and found the

similarities between the two to be so great that a name

change was unnecessary. The name remains in place to

this writing.

20

Basal Conglomerate - The basal conglomerate

frequently found at the contact between Tillamook

Volcanics strata and the Cowlitz Formation is highly

variable in both thickness and lithology. The thickness

varies from zero to more than 60 meters, the figure given

by Warren and Norbisrath (1946). In the headwaters of

the Nehalem River where it apparently follows the

straight line of a fault west of Timber (fig. 2) the basal

conglomerate thickness exceeds 200 meters. The

possibility exists, however, that normal faults have

repeated the section; normal fault scarps are evident in

many places along this portion of the river.

Lithologically, the conglomerate can vary from well

cemented boulder conglomerate to unconsolidated, poorly

sorted, angular volcanic sand. Clasts may be in matrix

support or in clast support. Much of the conglomerate found

in the river bottom west of Timber is poorly sorted boulder

to cobble orthoconglomerate in a volcanic sand matrix.

Typical conglomerates contain a mixture of tholeite basalt

clasts of aphanitic to porphyritic texture, and dark

greenish-black color, to lighter grey basaltic andesite.

Vesicular basalt clasts are usually present also. Any

attempt to generalize about the nature of this material is

thwarted by the variety which exists. The lithologic

descriptions presented in the Nehalem River Section

describe the lithologies involved in greater detail.

Lower Mudstone Unit - The composite section

21

produced for this report (fig. 16 ), has a thickness of

approximately two hundred meters for this member. This

agrees well with the Quintara Watzek 30-1 well logs (Mist

gas field, 17 km. to the north) which indicate a unit

thickness of 210 meters (Olbinsky, 1983). This figure also

agrees with the "typical well section, east Nehalem

Basin" of McKeel, (fig. 1 1983 p. 3).

This unit is described as a shale by Warren and

Norbisrath (1946), as a sandstone/mudstone by Olbinsky

(1983), as the lower sandstone member by Nelson (1984)

and as a siltstone unit by Van Atta 1971). This author

found the unit to contain primarily claystone at the base,

grading upward into a long sequence of mudstone, and thin,

laminated, interbedded siltstone and fine sandstone beds.

The unit is organically very rich and it has been

suggested that it is the source rock for the natural gas

accumulations in the nearby Mist gas field (Bruer, 1980).

Lignite laminae occur prominantly in the upper portions of

the unit, and the dark mudstones and siltstones of this unit

were observed by this author to mold· like cheese when

stored in air-tight cartons. Cowlitz mudstones have been

shown to have hydrocarbon contents exceeding one percent

22

(Armentrout and Suek table II, 1984). Vitrinite reflectance

values are low, howev~r, indicating that the thermally

generated gas at Mist probably has a more distant

provenance.

The color of the sediments in this unit are pre­

dominantly dark grey in the massive siltstone units.

Claystones were generally lighter grey, even bluish, and

the laminated sandstone/lignite/siltstone. units were

variable with often marked contrast betwen light tan

arkosic sediments and darker grey mudstone and lignitic

layers. Weathered samples were often a dull yellowish­

brown color which tended to obscure rock types in river

banks and roadcut exposures.

Paleontologically this unit is rich. The finer grained

sediments yielded most of the foraminiferal species

found in this study. Megafossils are abundant also, best

represented in this report in the Sunset Camp Section.

Trace-fossils such as Chondrites and Helminthoidea are

also found in this lower mudstone unit. Leaf fossils are

reported in the unit by Jackson(l983) but were not

observed by this author.

Nehalem River Section

A stream section was selected three miles west of

Timber in the upper reaches of the Nehalem River (little

more than a shallow creek at this point) (figs. 2, 5). This

S"DI:/

,,,,.,.,, ocr 0

NOID'3S 'H'3Al'H W'31VH'3N

NEHALEM RIVER SECTION

SER ES STAGE ZONE FAIJNULE FORMATION jiZ &ai5E!1 ~LITY

~ z :..:: < z z :.i.l

:i -, ... ::.:i

"" v f:: < z :;;: 5 <; I

::.:i < z ~ er: i;.:.J < < z

:-.J z ~ I.;.; ,.... _, ~ ::z:: ~ ~ < u..

0 ,.... z ...,, z E-~ ~ u.. 5: 0

I ~ :..:: ~ c... l5:: z ~ -... ~ < z :::; :::::;

5

T 30m

1

FIG.6

N E-:i :: 0 :..;

:..:: Vl

~~ ~z <<

g~

A257

~ bedded, ns!u1m grained, poorly inlurate'.I, aelitJD grey fresh, ~ weetrered, microfossi.liferous.

~ bedded, IJBiiun grained, poorlv inlurate'.I, naliun grey freSi, ~ weat!Erei, rai.crofcssiliferous.

~bedded, ne.i.i\Jll graiml, poorly inlurate'.I, neii\Jll grey fresh, re:ldi3l-bro.n

AZ~ weat.!Ered, carbonaceous, microfossiliferoos,

~ly bedded to llBSS!.ve, fine graiml, neliun grey fresh, ra:!d:ish-brown weetml'ed, microfossiliferous.

A255 ~ bedded, fine grained, ne:litJD blue-grey, "chippy" weathered aP{mI'BOCe, microfossiliferous.

A254

~ve, fine grained, ne:litJD grey-bro.n, pelec)'JX)i awnds, mi.crofosill.­iferous.

in

in

~ poorly sorte:l, angular, ncn-1.rdurate'.1, black, well be:lded. caaj.aiera~rly sorte:l sard-pebble c:.lasts. ~ve volcanic, poorly lllrt.ed, well :ln:lurated, olive green freti. caiglane:rate-l:esaltic pebble cla.sts.

A253 siltstme-Yol.canic, carlxxa:EoJs, micro-fossiliferous, . ~. poorly !llrtal. ~e-c.obble ardesite & beslllt ccntact-Tillsn:xX Vol.cani.cs-07wlitz Form.

24

25

;:... first flows of Tillamook Volcanics basalt

11 ~ microfossiliferous silts (J

greenish black angular

~ volcanic sand grey green coarse indurated volcanic sandstone rJj

rJj

indurated basalt rJj

boulder conglomerate m with sandstone matrix (J

~

5 blue-grey laminar z clay stone

~ z m

flif'.LYll//li1 :!:! ::c: p ....

> mud stone ~ m

~ ~ ~

< t!'j

highway bridge ~ rJj

~ ~

massive microfossiliferous 0 mud stone z

3 ~ 8 @ ~ ~ 3 3 3 3

26

section was selected in part to represent the Tillamook

Volcanics - Cowlitz Formation contact. Other desirable

features of this traverse were the excellent exposures of

basal conglomerate, as well as the fact that the dip

direction of the strata was found to occur at a fairly low

angle to the axis of the stream. This nearly optimum

relationship of dip direction to stream course found at the

northwest end of the traverse is lost to the southeast,

however, where the section was terminated.

The Nehalem River at this point is obviously not

strike-controlled as it is in the Sunset Camp Section, but

is instead fault-controlled. The stream course is

exceptionally straight, and in places cuts steep-sided

"slots" in the hard conglomerate of the lower Cowlitz

Formation. This strongly suggests that it is followingfault

gouge zones. Also, intersecting normal faults are apparent

in the northwestern part of the section. These are

indicated by distinct faultline scarps (to 1 m) as well as

the linear configuration of branch streams which

apparently follow these faults.

The Nehalem River Section is approximately 1800 m.

in length and represents a stratigraphic thickness of

about 275 m. (fig. 6) Dips are generally southward and

vary from 14 to 17 degrees (fig. 7).· The stream bed is as

wide as 25 meters where the river widens in the soft

sediments at the southeastern portion of the traverse, to

as little as 2 meters where it cuts small gorges in the

conglomerates and basalts of the northwestern portion.

The stream bottom is largely obscured by a bedload of

basalt cobbles and small boulders.

27

The Nehalem River Section presented a highly varied

and interesting sequence of strata. As indicated above,

the section can be divided into a volcanic and conglo­

meratic portion and a claystone-siltstone-mudstone

portion. The volcanic, conglomeratic segment can be

further subdivided based on the strikingly variable nature

of the beds which one encounters.

The volcanic conglomeratic portion of the section

represents 90 meters of strata. It contains sedimentary

beds of fine siltstone to well-sorted large boulder

conglomerate (1.5 m). It is roughly comprised in equal

proportion of well sorted cobble to boulder conglomerate

and poorly sorted volcanic sandstone with pebble to cobble

inclusions.

The traverse begins somewhat arbitrarily with a

thin, massive basalt flow exposed in the river bank.

However, subrounded to subangular cobble to boulder

conglomerate is exposed upstream for at least another

half kilometer from this point. Upstream, near the S & P

railroad Cut Section (fig. 2), conglomerate appears again,

suggesting a great thickness of this member in this

locality.

Approximately 25 meters downstream from the thin

basalt flow which marks the beginning of the traverse,

appears a massive, thick (6 m.) bed of dark, greenish­

black, unconsolidated, poorly sorted, extremely angular,

coarse basaltic sand. This material is somewhat

weathered and consequently impermeable.

28

Below this appears a very well indurated, calcite­

cemented pebble to cobble conglomerate which extends for

some 60 meters. This is followed by a light olive green,

poorly sorted volcanic sand which continues for another 50

meters. Subsequently a short sequence of pebble to cobble

conglomerate appears, followed by a striking layer of

loose, black, coarse, basaltic sand. Crude bedding planes

are apparent in this bed, but the orientation of clasts is

random. This sand is chemically fresh and highly

permeable with a stratigraphic thickness of less than 3

meters (fig. 6).

A short covered interval gives way to a tan, fine­

grained, well bedded siltstone from which foraminifera

were isolated (PSUA 253).

A pebble to cobble conglomerate is exposed for 10

meters. This gives way to a long (450 m) sequence of

poorly sorted, light olive-green volcanic sand. This

material is well indurated with calcite and clay cement

and in places forms cliffs and benches along the river. It

is unfossiliferous.

29

Another short covered interval of 30 meters down­

stream reveals a conglomerate series which is unbroken

till the laminated claystones of the fine grained sedimen­

tary sequence appears some 110 meters below. The size

of clasts in this conglomerate grades upward from pebbles

in the lowermost portion of the unit (upstream) to huge

boulders (1.5 meters) in the central portion. A cobble and

small boulder conglomerate appears near the top

(downstream). It is here that the stream cuts deep slots

in the bedrock and where exposures are best in nearly

vertical cliffs. Also faults are strikingly apparent here, in

part because the rock is so indurated and therefore

resistant to erosion.

Claystone-siltstone comprises the bulk (185 m) of

the Nehalem River Section (fig. 6) At its base it is well

bedded, even laminar in places as well as being very fine

grained and clay-rich. Its color is bluish grey. It is

microfossiliferous, including sample sites PSUA254, and

PSUA255 (see checklist for species occurences).

The uppermost portion of the unit shows much more

sedimentary structure than the underlying massive

siltstones and clay stones. This probably reflects a higher

energy environment of deposition. In addition to the thin

laminated strata, mentioned above, sandstone layers

exhibit ripple cross-lamination. Jackson (1983) also

found structures resembling hummocky cross strati­

fication on a small scale here.

Sands and silts of this unit are micaceous, con­

taining both biotite and muscovite. The sands are com­

positionally mature (Van Atta, 1981) and moderately well

to well sorted. These sands are not very permeable,

however, (Armentrout 1983) due to the inclusion of

volcanic lithic fragments.

30

Sandstone Unit - The sandstone unit of the Cowlitz is

typically a highly permeable stratum (averaging 200 md

to 1500 md) (Newton and Van Atta 1976) and is the target

unit of the Mist gas field. The unit is composed of fine to

medium grained micaceous, quartzose sand. It is remark­

able by virtue of its lack of lithic rock fragments and clay

material.

This unit is very poorly consolidated, leading to

frequent slumping of incompetent banks along roads and

streams. This yields many fresh exposures wherever the

upper Cowlitz outcrops.

The unit is best exposed in the New Road Slump

section of this report. Here it is clearly separated into

two subunits herein called the "Clark and Wilson sand"

(lowermost) and the upper Cowlitz sand. These are

separated by dense claystone layers which effectively

isolate them from one another in the gas wells of Mist

(Townley, oral comm. 1984). Olbinsky (1983) and Nelson

31

(1984) also distinguish between the two subunits based

on petrology. They refer to the lower subunit as the

"zircon rich" sandstone and to the upper as the "epidote

rich" sandstone. In the New Road Slump section the unit

is at least 150 meters thick, but this appears to be highly

variable since the Sunset Camp Section nearby offers less

than fifty meters of sand. Additionally the sandstone of

the Sunset Camp Section is less recognizable as a sand

unit in the field, being finer grained and much darker.

Rock Creek Section

This section was included here because it represents

a typical sequence of sediments of the transitional or

heterolithic strata intermediate between the upper

sandstone member and the lower mudstone members.

Large displacement normal faults are involved in this

section, particularly at the Tillamook Volcanics - Cowlitz

Formation contact where upper Cowlitz sediments are

faulted against Tillamook Volcanics flow rock (fig. 10).

This gives the appearance that the stratigraphic column is

being "stood on its head," as shown in the cross section

(fig. 10). Also abrupt attitude changes near the town of

Keasey (fig. 8) and slickensided samples from the stream

bottom indicated faulting, demanding. a termination of the

traverse. Stratigraphic control could not be established,

leaving this section as a "floater."

.,._ OH 0

A J_

" .-l.-

"" ' , .. v .. _.__

NOIJ.::J3S )133'8:) )IJO'M

ROCK CREEK SECTION

S£R ES STAGE ZONE FAUNULE FORMATION

~ z ~ z ;...: ..., t...: u < a:: < ...l

z ~ < z B z w ~ @ ::.::

< u.. z ~ ~ ...l c.. I

::.::: u z :...;

Q Vl

< z :::; :i ~

T 10rn

1 F/G.9

< z ...l ::; ~ 1= z ... ...l I Vl ... Cl c iiS c

Vl

!:::' z < u ~

8 :; < ...l ...l

!==

N !­:i

~ u

il!Jli,Jiiiiiliiihllliilhi.i.i!ii;; .. !I t.o<'At.JTY ruined railrcsd trestle.

·=-:-=-,-'::-:_-:-.:..-c-.:::~--~"".l A247 - -·-·- - -·--=--=_:_=.....:....::-:..:::-:..:::~:::..7-:_. - -·- -- -·--· - -·- -· -·--·-·-- -·- - -· -:-...:_-_7.,;_~~-:'~7'~7'

A248

:.-;

£~i~1Y~t~Ut~~\1~f A249

~;11is~ A250

A251

~f$f ~~~~;~~l~£~ft~:

A252

tasalt~, bra:.c:iated flCMS.

fault-large displocarent oonal.

~ve, poorly irdurated, fine grained, very mi.caceoJs, light grey. ~bedded,very friable, aeiiun grained 'very mi.caceous. siltstme--.e.l.l l:alde:I, very friable, aeiiun grained, mi.caceous.

~ve to bedded, loe1l indurated, mi.caceous,

sil~J.am:.nated, friable, nalitJll grained, micaceous.

sil~lalrinated, friable ,micace:ius cartxroceoos , naliun grained.

sil~lalrina~. nnlerately in­durated. !!BiirnKOOI'Se grained, li~t grey fresh and W'itrere:i • swrlstrne-1.aninated, ...,,U indurated, poorly micaceous. san:!stcne-ims i ve aro cross bedded, poorly indurated, ae:!iun grained and ..-theroo, large (Im) an:.retioos. ~ bedded, friable, l!Ed­i\Ill grained,

slickenal les here. sil~ bedde:I friable aai-­illll grained, m1.c.aceous: medi.ll!l ~

sill:st:me-m!ssive, friable, ccerse grained. m1cace:us. san:!.st:ae-bedda! cm:reticrary. nalil.Jll grained ,rx:n-ml.ceceous ,quartzase 'very light grey. sil tsta1e-nB.ssi ve, a:n;retionary, catil.Jll grey.

33

34

Ill ,... c.n 8 @

llJ llJ 0 0

0 c.n 0 0

3 3 3 3 3 3 n i:;:::

trestle ~ aa flows of Tillamook Volcanics er;

er; dark micaceous fine grained sandstone er;

~ n --3 ~

~ :?:! ~·· .': .. ·.:: :··· :::.\S~·j ~ ~ 0 \\ ~\· .. " ..... \_,\ siltstone

~ "Clark and Wilson" n sand ~

n ~ tT'1 tT'1 ~ er; ~

sandstone n ~

concretionary shelf a z

The Rock Creek section is located about fifteen

kilometers southwest of Vernonia, and adjacent to

35

Keasey. The type section of the Keasey Formation was

established downstream northeast of Keasey, just a few

hundred meters from the termination of this section. The

stream is clearly strike controlled here, exhibiting linea­

tions along a northeast-southwest axis (fig. 8). Dips to

the south are quite variable from a minimum of 7 degrees

to a maximum of 25 degrees. As mentioned before, dips

are opposite to that expected. That is, it would be

expected that sediments dip away from the volcanic high

to the south as they do in other parts of the study area.

This leads to the conclusion that faulting is a serious

problem in this section, and also that measured section

thicknesses are highly questionable. The section's rich

foraminiferal representation, as well as good exposures

of representative lithologies, however, justify its

inclusion here.

This Rock Creek Section traverse covered nearly two

kilometers, but meanders along strike-controlled

portions of the stream and the inclusion of Tillamook

Volcanics flow rock combine to yield a relatively small

(105 m) stratigraphic thickness of Cowlitz Formation

strata.

The traverse begins at a ruined railroad trestle with

its foundation on the banks of Rock Creek. Although the

36

volcanic rock exposed in the creek bottom has been

described as a conglomerate (Van Atta, 1971) its poorly

distinguishable clasts are subangular, very similar to the

matrix and probably represents a blocky basalt flow (aa).

This blocky basalt is found downstream (about 250 m) to

the fault contact with the intermediate to upper sand of

the Cowlitz Formation. Above this contact, in a road cut

less than ten meters above the level of the creek, the

clean, very light tan arkosic sands of the "Clark and

Wilson" informal member of the Cowlitz Formation

outcrop • The sand at the contact, however, is fine

grained, medium grey, micaceous, and somewhat "greasy"

with clay. This sandstone is very friable and is found in

well defined beds (1 m). It becomes softer, less

consolidated, and lighter in color for 140 meters

downstream. One concretionary shelf (2 m) of massive

micaceous sandstone intervenes at sixty-five meters

from the contact. At one hundred fifty three meters

downstream, the sandstone again becomes medium grey,

clay-rich and well indurated. Plant fragments and lignite

layers are incorporated in this material. A very coarse

grained lithic sandstone appears at 180 meters. This is

replaced by finely laminated micaceous, carbonaceous

sandstone which is further characterized by ovoid (10 cm)

concretions, and intense bioturbation downstream

(downsection).

A series of grey, micaceous, laminated, poorly

consolidated foram-rich siltstones were sampled to a

37

point 510 m downstream from the Tillamook Volcanics -

Cowlitz Formation contact. Here a high, nearly vertical

(10 m) cliff in the stream bank reveals very planar, yet

intensely burrowed thin (2 cm) beds of medium grained

well indurated light grey sandstone. Spherical to ovoid

concretions of large size (.7 m) appear at the base of the

exposure. Arkosic, micaceous, medium sand outcrops in

the stream banks for another one hundred meters where

the bedded sandstone sequence is repeated by the

doubling back of the course of the river. This gives way

to a fairly long sequence of microfossiliferous silt­

stones which extends to the townsite (just a few old

railway station buildings) of Keasey.

Below Keasey the siltstones give way again to

medium to coarse grained arkosic sandstone beds which

are frequently well indurated to concretionary. One

concretionary layer is 25 cm thick at 1600 m. from the

Tillamook Volcanics - Cowlitz contact.

Sandstones give way to another sequence of mud­

stones which extend downstream to nearly the end of the

traverse. This sequence was productive of Foraminifera.

Samples PSUA249 through PSUA252 of this study were

selected from this sequence. The sequence ends with a

concretionary layer (.3 m) in the river bank, the

38

orientation of which indicates a nearby complicating fault.

This is underlain by a medium to coarse grained arkosic

sandstone found just downstream of PSUA252.

New Road Slump Section

Ironically this section yielded virtually no fossils

of any kind and might be considered inappropriate for a

paper dealing with the biostratigraphy of the Cowlitz

Formation. However, it is included here because the

section offers a virtually continuous vertical road cut

exposure of relatively unweathered upper Cowlitz

Formation sandstone. Also the section includes the

Cowlitz-Keasey contact, giving it stratigraphic control.

Sedimentary structures such as soft sediment defor­

mation, trough cross bedding and channeling are much

more readily observed here in a road cut than they would

be in a stream section.

The stratigraphic thickness of this section is

reported here only approximately as 150 meters. This

lack of confidence is due to the close proximity of this

section to the Rocky Point Fault (fig. 12) and because of

local landsliding activity. The traverse is 1350 meters

long (fig. 11), following a newly cut Longview Fibre Co.

logging road. The banks of the roadcut are virtually

always linked at their bases, offering nearly continuous

exposure of bedrock. At the eastern end of the traverse,

... z

z .. :a ~

z.

....... , "\

probable fault

- a-..

NEW ROAD SLUMP SECTION

*

' ~l 0 150 500

.,.,.,,

FIQ.11

39

,. ,, '4N

,. ,. +. llr Point

.,..,

unconsolidated

~''"(

:!! p ii;

. ".1

poorly consolidated micaceous sandstone

soft sediment deformation pl.6

probable fault

".".

..... ~i·' .' ·;. ,i . . . .. '// ..

• ·. 1111 .

" I. 'l; . . ~

.... Ii ,1 .

i. ff .: lj,1 ....

.· ·./,i ·j

"greasy" shale parting pl. 7, 8

unconsolidated massive sand pl.9

"·. .:!. t . . . J.;f, .. . . ... ;1 . ·; z1 ". · ·::; 7 · ' ·/ I : :"11 'J · ·/ zi; ; ..... / . .... f-1111 I . ".. ·I· I ... J '// . . . " 11!.~"I. /. : · · z. · '. / /·f;l;/; /1

"chippy" mudstone pl.10

. ./1 / · · ·'11u'z'1· ·. · ,, . . . . .11pN111,

.h ;: . . : . : -.H1zzz~ld . ~ · · u;I Pt' z1 // · . -. . . 1 ·/ /1.f/:/f.'11.

~~. . · . ·" · ·~ H~J.f.~zt~~ ~1 . . " .. .. ~·1 ~Zz~~zZ~'., . I ,.1/:1/;;Y

· .· · .. · ·;yilJ?Bl'1?/ " . . . . . ·,IA'/,' zl.~ZzzlZ'/,Z'/ · . . · · · 111.z z·, zr "' · . . . . · · ;' p,z-1Y,z1,r,z

· · · · .. /1.f1,z1·X~Z1 . . '. II~Z'f,~'l,~1.'1/ .. .111.z~~z1.~1r • . zl,~l'''/,1.~, ,,,~1t1!.

'·Z'/.

...,.

hard Keasey mudstone

40

n ~ CJ) VJ

~ n ~ ~

~ ~ z ~ ~ ~ u rJ'l

E ~ ~

rJJ

~ ~ ~

~

on the soutl1west side of the road, a very large slump

exposure of the lower Keasey Formation occurs. Removal

of most of the slump debris at the toe of the slide has

further improved the excellent exposure here.

41

The traverse begins at the "t" intersection of Rocky

Point Mainline Road where it intersects Fall Creek (fig.

11, upper left). Stratigraphically tt1is point is well into

the thick upper sandstone informal member of the Cowlitz

Formation.

At the beginning of the traverse, orange weathering,

micaceous, arkosic upper Cowlitz sands are exposed in

the first series of banks along the road. The sediments

are light grey in fresh sample, and are non-indurated,

apparently held together by little more than the cohesion

of water and traces of clay on grain surfaces (plate 4).

pf.4

42

The sands have a distinct iodine or "seashore" odor. The

strata here exhibit both laminar bedding as well as

subdued cross stratification.

Proceeding uphill along the section road to the

southeast, the sands become interstratified with blue­

grey claystones. Soft sediment deformation is strikingly

exhibited here (Plate 5), where density contrasts between

the two sediment types as well as rapidity of deposition

are indicated.

p/.5

These clay beds are further characterized by thin black

laminae of lignite. Leisegang banding is a common feature

44

here, often confusing true bedding orientation and

sedimentary structure. Plate 6 for example, appears to

indicate inverted, convex-up cross stratification, whereas

the real case is that migration of limonite was controlled

by small fractures in the beds. Frequent small displace­

ment faults occur in this lower portion of the traverse

(plate 7).

pt.a

Interstratified heterolithic beds give way to a thick

sequence of cross-bedded, very poorly indurated arkosic

sand which is exposed in every bank to the approximate

45

midpoint (600 m) of the traverse. Small bits of lignite

are found interspersed with the quartz and feldspar

grains of these beds. At this midpoint, another clay rich

parting occurs between sand units. This thin claystone

unit (fig. 8) incorporates what appears to he a fine

grained siltstone but this may in fact be a highly

weathered dark tuff. Although heavily scrutinized, these

fine-grained rocks disappointingly yielded no micro­

fossils.

Above the claystone parting, massive, buff colored,

almost completely nonindurated quartzose, micaceous,

arkosic sand is exposed for a stratigraphic interval of

approximately 50 meters (plate 9).

pl.9

46

The well-bedded sediments of the lower sandstone

member are replaced by a nearly structureless mass

which is exposed in high (10 m.) embankments. Only very

subtle planar bedding is noticeable. Other sedimentary

structures are absent.

The final portion of the section is comprised of

mudstone which grades up into the overlying Keasey

Formation found in the slump/landslide. This mudstone

was very deeply weathered to a "chippy" talus material

(plate 10) in all exposures.

pl.10

48

Again, intense sampling and excavation yielded no

microfossils. The first recoverable foraminifera in this­

part of the section were recovered from the mid-portion

of the slump, which yielded such mid-Refugian species as

Pseudoglandulin inflata (Borneman) and Melonis halkardi

(Cushman).

Sunset Camp Section

This traverse along the Nehalem River from its

intersection with the Sunset Highway at Timber Junction

to a small bridge about two kilometers upstream

represents the thickest section (493 m) of this report

(fig. 14). It is also the most reliable section. This is

because no obvious large displacement faults cut it (fig.

15), nor are landslide blocks involved. Strike directions

are uniform to the northeast, and dips to the southeast

range between 14 and 18 degrees. Coarse basalt cobble

bedload obscures much of the river bottom, but, as with

the Nehalem River Section and the Rock Creek Section of

this report, it was usually possible to secure a sample

somewhere in the river for every twenty-meter interval

of the traverse.

Much of this same section (but not called by the same

name) was carefully measured by Van Atta, (1971) and

described in great detail. Before Van Atta, Warren and

Norbisrath (1946) described the geology of the bedrock

here and determined the Cowlitz-Keasey contact which

t:l'Dl.:I

Oli/0001

0

~ .• I '

NOIJ,:J3S dWV::J .L3SNf1S

SUNSET

SERIES STAGE ZONE FAUNULE FORMATION

KEASEY

:;; z ::.:: z ""' --,

Q.;

;.i.;

:.,)

< < z ~

< ,.., ~

;::i ~ z u z IS • < 5 • ;-z N z ...J

""' ;: ~ I ?; u './") ,.... < 5 ;::: 8 '-'

"'" z !-

~ c,.; ~ =:; 0:: ~

I

::.::

~ .,,; ......

~ < z ~ ::::l ;::i a::

T 50m

l FIG.14

50

CAMP SECTION

-.~-.;:_~ ....:.-::._~ .:...:.-·~-:: _. - -·- -·- -·-·-=;~~~"i~~~~~~~=

~~~~~i~t¥¥:~

DESCRIPTION

A267 siltstone-<mss1ve, ""11 indurated, fine grained naHDi.cac.eou.s, dark grey freffi, re'.1--bro.m weatrere:l, rn:i.crofossiliferoos.

silt:stme-m3SS1ve, p:xirly indurate:i, fine gra.ine:I, inic.aca:>1Js, quartul93, light grey fresh. red-brown ..... trered.

safl'.!y siltstme-l!Bssive, poorly indurate:l, micac.eou.s, quartzose, maditJD grey fresh, yellor-bro.m ""'3trereci.

sarrlst.ae-<ll9ive, poorly in:lurate:i, fine grained, very micac.eou.s light grey fresh, yellor-grey i.mthere:l. siltstcf'le-<llaSSve, ""'11. irvlurated, coorse grained micac.eou.s grained, rnicac.eou.s, light grey fres'l, yell""'ill"ey i.ea:J>ere:J. ~rly indurat.e:l, fine grained very m:i.coceous, q~, madilJJ grey frat., re:l-brown ""'3trerei. Sllrlstroe-elterrutely JXlOr to very ""11

A266 :irdurate:i, micac.eou.s, sandstme-<IBSSive, poorly inlrmted, fine grained. micac.eou.s. siltstooe-<mssive, JX>Orly induratel, fine graine:l, micac.eou.s, microfossil iferrus,

A265 mill.IS< rich •

siltstone-<mssive, m:x!erately ""11 i.nduratel coarse grained, mi.caalous, lllicrofossil­

A26• iferous, milusk rich, na:lilJJ grey fresh, yellor-bro.n weatrerel.

A263

~ve p:xirly indurate:l but erosioo vesistent shelf-forner, coorse grained, volcanic c1asts, clast sup(Xlrt, !XJOr s:irting • siltstooe-ililSSive, poorly :irdurate:l, coarse grained' micac.eous' dark grey fresh. brick

A262 red ""'3there:l, nticrofossiltieroos, milusk-

~ve, coarse grained, mi.cacoous !lli.crofossiliferous, mlluS< rich. sandstme-<mssi ve, \Ell :i.Murate:i, coarse

A261 grained, lithic angular clasts, sil tstme-miss:i ve, m:xleratel y indurated, coarse grained, micac.eou.s, dark grey freffi,

A260rel~ ""'3there:l, micrfossiliferous, nolluS< rich,

A2r9

S31ldst:me-<:oase grained, lithic, calcite caElted. dark grey fresh, light grey weathered.

~ c;;

U.S. Highway 26 Bridge >(Timber Junction)

calcified coarse basaltic sandstone

siltstone

very coarse angular basaltic sandstone forming shelf at cor'luence of Nehalem River and Louisinant Creek

V/llll!lllf!l:J calcified mudstones forming shelves

dark grey poorly sorted sandstone

mud stone

silty sandstone

Keasey mudstones f: ··."· "fllll·f·t. ':1UlllJll t=

Nlogging road bridge

~ ~ ~ ~ i ~

51

n ~ V"; V";

V"; tl1 n ~ -~ 0 ~

V";

c:: z V";

~

9 ~ ~

C/'J tT1 n ~ -~

52

intersects the course of the river using Foraminifera as

well as noting collection sites for megafossils in the

stream banks. This author was aided by consideration of

this earlier work.

This section has one flaw; it is probably somewhat

atypical of the upper Cowlitz Formation in the upper

Nehalem River Vally. That is, the sandy silt and

sandstone unit toward the top of the section is dark,

"dirty" with ash and clay. Normally this sand unit is

well sorted, mature, and appears light tan or very light

gray in outcrop. Foraminifera are absent in this unit as

they are in other upper sand outcrops of the Cowlitz in

the study area. Medium and fine sand particles of quartz

and feldspar grains predominate, and the position of the

sands in the stratigraphic column is similar, but the

similarity ends there. This section may represent a local

facies change, possibly a less energetic environment of

deposition, or one further from clean sediment sources.

The traverse began at the Sunset Highway bridge

(fig. 13). Here, in the stream bottom, rather massive,

dark gray beds of micaceous siltstone and mudstone of

the upper lower mudstone informal member of the

Cowlitz Formation outcrops. Immediately to the south

appears the first sandstone, a coarse grained, calcite

cemented (white crystalline matrix) volcanic material

which forms a strike controlled, thin (.4 m) shelf which

53

cuts the river at nearly a right angle. Such shelves as

this one were to characterize many portions of the river,

the course of which is clearly strike controlled (fig. 13).

Strike control is most noticeable in the northeast­

southwest lineations near the confluence of Lousinont

Creek and the Nehalem River approximately one kilometer

upstream from the Sunset Highway bridge.

Beyond the sandstone shelf a long sequence of well­

bedded microfossiliferous and mollusk rich siltstone

outcrops for a traverse distance of about two-thirds of a

kilometer to the confluence of the Nehalem River and

Louisinont Creek (fig. 13). The stratigraphic thickness

represented here is one hundred twenty five meters from

the Sunset Highway. This siltstone is dark gray in fresh

hand sample, rusty brown in weathered sample. It is

medium grained and quite micaceous. The unit is

relieved by just one thin (3 m) shelf, forming well

indurated sandstone which appears at sample site PSUA

262 on (fig. 13), about one half kilometer from the

bridge, and 96 m stratigraphically from the stratigraphic

columns base (fig. 14). This sandstone is poorly sorted,

massive, very coarse grained, volcanic, angular, and

olive green in both fresh and weathered samples. A short

series 2 m of resistant sandstone ledges mark the end of

this sequence at the confluence of Louisinont Creek and

the Nehalem River.

54

The next sequence is also of siltstones which out­

crops to the approximate position of PSUA266 where the

river follows a series of erosion resistent sandstone and

siltstone shelves, which control the course of the stream

for several hundred meters. These siltstones are

typically massive, poorly indurated to well indurated,

micaceous, dark grey in fresh sample and reddish-brown

in weathered sample. These sediments offer many

mollusk fossils as well as foraminifera and are cited by

Warren and Norbisrath (1946) as exceptionally good

megafossil collection sites. Clast size increases and

foraminiferal abundance diminishes upsection. This

portion of the traverse represents a stratigraphic

thickness of 134 meters.

In the next portion of the section, gray siltstones

become increasingly sandier, giving way to the gray

"dirty" micaceous, arkosic sands of the upper sandstone

informal member of the Cowlitz. As mentioned above

this probably is an atypical, hardly recognizable

equivalent of the "Clark and Wilson" sandstone. The

sandy silts and fine grained sands, however, do not

include the calcified, resistant material of the subjacent

sections. These upper sandy deposits are either poorly or

very poorly indurated or even unconsolidated as in "Clark

and Wilson" sediments. The color changes in these upper

section deposits to a significantly lighter gray

55

reflecting the higher proportion of quartz and feldspar

grains. As mentioned above, Foraminifera are absent, as

in the "Clark and Wilson" sand of other Cowlitz Formation

sections.

The upper segment of the Cowlitz Formation of this

section comprises 96 meters of the stratigraphic column

(fig. 14). Although samples classify as siltstones (Van

Atta, 1971), a variety of lithologies exist, including some

finer grained claystones and sandy silt as well as sand­

stone beds. These beds are also largely barren of fossils.

In color these rocks are light grey in fresh hand sample

and weather yellow-gray.

A detailed discussion of the Cowlitz-Keasey contact

at the top of this last portion of the section is included in

the biostratigraphy section of this paper.

Keasey Formation

The Keasey Formation was not the subject of this

study, but the lowermost part of it was included in

measured section including the Sunset Camp Section and

New Road Slump Section in order to establish their

stratigraphic position. This formation cpmprises about

700 meters (Warren and Norbisrath 1946) of tuffaceous

shale and mudstone containing many megafossils and a

large assortment of deep-water, largely Refugian, Fora­

minifera.

In hand sample the sediments of the basal Keasey

closely resemble those of the upper Cowlitz mudstones

both being gray, fine grained, poorly stratified rocks.

On close examination, however, the distinct lack of

mica in the Keasey Formation sediments marks the

Cowlitz Keasey contact. In the Sunset Camp section of

this report, coarser siltstone with much mica and

arkosic, quartzose sand of the uppermost Cowlitz For­

mation gives way to fine, slightly darker-grained

material with little mica. Lithic fragments occur in

both members but are strikingly more abundant in the

Keasey.

56

Kadri, Beeson, and Van Atta, (1983) used geo­

chemical analyses to indicate a change of provenance of

sediments from Cowlitz to Keasey time. They found that

Cowlitz rocks were enriched in mica, feldspar, thorium

and potassium, while Keasey rocks contained relatively

less of these constituents as well as more volcanic rock

fragments. A plutonic/metamorphic provenance of the

Cowlitz Formation and mixed volcanic/continental

provenance for rocks of the Keasey Formation are

indicated.

,._ II)

20

0m

10

0m

Om

SU

NS

ET

C

AM

P

SE

CT

K)N

CO

RR

ELA

TICX

\r O

F

SE

CT

ION

S

NE

W

RO

AD

S

UJM

P

SE

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ION

Kea-;e

RO

CK

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RE

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klN

Form

ation

CO

l.llMR

IA

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UN

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Q

UA

RR

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<. 'ow

litz F

orm

ation

~--· -

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FIG

.'6

NE

HA

LE

M

RIV

ER

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EC

Tl<

lN

S.& P.

RA

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UT

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~

~ " -I! I~ ~ ~ "' ~I~ ~

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lil.i ..

!:i "'

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l T

illamook

Volcanics

CHAPTER III

PALEONTOLOGY

The Foraminif era

The Cowlitz Formation in the study area exhibited a

fairly limited number of species of Foraminifera. Forty­

four species were identified. These constitute 33 genera

and 14 families. The most numerically prominent fami­

lies include: Rhizamminidae represented by Bathysiphon;

Lagenidae, represented by Lenticulina, Dentalina, Lagena,

and Marginulina; Heterohelicidae, represented by Plecto­

frondicularia; Buliminidae, represented by Bulimina,

Bolivina, and Trifarina; Rotaliidae, represented by

Gyroidina and Eponides; Cassidulinidae, represented by

Globocassidulina; and Anomalinidae, represented by

Cibides.

Other Fossils

Although the Foraminifera were of primary interest

in this paper, a number of larger fossils including those

of gastropods, pelecypods, decapods, brachiopods, and

fish teeth were collected in several localities. The most

productive locality was the Columbia County Quarry,

CHECKLIST OF SPECIES

FORAMINIFERA

.Uirncrnhim cf. :T?.cro~torn of K1u l%S

N-lfrer·

.)rnn:x1lSCcLS CCXlTibsi

'.i:Uw~j ffi>rl eo:en.ica ( .:u..o:;il!IJD & C. D ~ Fnnnn

t'oidid :1c(L.!e! ---zcw;. 8. S:_:(JPJK'k)

Po!ivina basicenta G.t.shn:ID f~ St <lf"~~

2olivina klFinpeJ.1 i

i.ed<

Puli.rrina. s."' .. hm::kl

ih:k

Ceratobti!irninn '>•.'asriburnc~ (h,hr;rn1 & SchellCk

Cl b i.cides ..§2·

Cibicirles iJ:ii LeYi ~---

Cibicidc~ nat land i Peck ___ _

Cvclcrr:tin2 p::1cif.L::.a Ee:k

I): ~n t.a J ·i !1-J (hlf>f!nbuni.

:)::}1La.l ln;.i omr:i;rii:­

cl'Orbibn::

? F.ggcn: 1 Li

Ep:xlidcs !rcxic.sru (Cc<;il1EJ1)

G 1 oi:D:a.s..sidul:i.r.a g lotos.1 (Hmt.ken)

Globobulinina so.

Glooobtilimi.na pac i E:ica n~i.'Tl1111 ....

FIG.17

Sunset Camp stK:tlon

"I" "' "' ii: ~ "" ~

.. "' "' "'

• ABUNDANT

.. ~

.. ~ "' "' "' "I "I" "' "' "' (.ft 0) I .....

Rock CrHk section .. ~ .... "I" & ~ "' "'

.. , .. :s =::

.. 1 .. i:i .. r:r: 1 .. ~l I'.) N t.,> N ~ fro.) 1') ,_,

~ ~ ~ Ill g: ~ Ill ll

fl MODERATE NUMBERS f"01 RARE t:1l

CHECKLIST OF

GlobuJ.inD land1.~si ~·iaK.lb:.in)

(~,uttul:ind irre-Qt~la.ris

~-bi.gny)

G\'roidi.J1.:: ccndon i (CusfTam & Scht-JK k)

Gvroidina orbicu 1 ar: s v::ir. plnn.1ta

Cusfr11;:

~§2.·

hc:ti~u I ha §!!.•

lenLiculina ~1£!:!i Church ·

T.enlicul ina lr1on18.U1s (J'Orbign;·)

lL~nL i cul i rn texanus

Ulishmn K App Lin)

:hruirnJir111 ~D.

\h.s:-::i1 i;v.-1 .::L·

,1cx :c~~J n d .32.·

Pl ec!..:.)f n.i:-1(l i cul.aria !XlC.kt.r:-:J i. - Cushnn.n

P.seudo~ 1 a~1dd i na ? sp ,

PselllL)gland1J. i:•:i cvaLa

~J.1···>Lm·m

PR"'ttdohastit:eri;i:l m:i.:.ni (Cole)

Pseudon<.x!os:rr la ~ 0.Lc.;fffHn 8, . .\:;Jp l ill

Psc{Jdonode>...S2Tia ccnica ('.\e:qetx>re:1)

FIG.17

Sun.set C.mp s.ction ,. ~ "'

.. N g

~ ~

,. N O> N

II ABUNDANT

,. fl ~

.. ~

N N "\"' O> "' O> ....

SPECIES

coic •rry Rock Crttek section Nehalem s.ction

~ ~ "'I" N N .... .. "'

N N "I"' g: ~

,. ~

,. N

~

fl MODERATE NUMBERS

,. ,. .. ~ ~ ~

,. N

~ ~ ~

.. ~

p:::::] RARE Lill

CHECKLIST

Sunset C•mp section

0.1in011ilr.cuti.na .:it·

'.hinquilocc! l lna lbnna & Han

S:Jraccnar i a h.-111

Cuslmm

Stilcstcr.Y.' 1 lJ s

Trif.:riri:.1 .hcr,rtl l:l?<Ck

U\igcrina sp.

~·a~.i:·;u ! i.n •. 1 21!.·

Va~i:u.i l opsLs 53

(Jbnm & ll

~-2L·

MOLLUSK A

.·\ci La d{.'!..:Jsa C,onrad

irr~r·L:"lli.s

~ i

)>

"' "' <D

,:

Brac:h i 1.x~nnLe!-:> ':oi.d i tzen.sis I

Qgy.ptraro sp.

WmL-.; vndercnsi::; ·(Yieaver & Pn 1:-rcr)

D-..T.to I i tri ~·

~Jitalirnn petrir.'ota ((;nbb)

Epi t.0ni um condoni (furbt'll)

)> )> )> .. )>

"' "' "' "' "' ~ "' "' !:l ?; - "' f<:< I;<.

'

1:7 I>:: ..

,;:.

'

'•

I·.::

'

FIG.17 • ABUNDANr

)>

~ "'

·:·,

>

I

I I I I I

I i I

I I

OF SPECIES

- - cOic Rock Creek se-ction He/la/em $f1Ction ruBnj

)> )> )> )> .. )> )> .. )> )> .. )> .. .. .. "' N "' "' "' "' "' N "' N "' "' "' "' "' g: "' ... ,.. ... g; !:: "' "' "' "' "' "' g; ... ... ... a> <D "' (.> • "' "' ... "'

'i;::

f~: I I ..

I I I

I I I i I

I I I :· !

••••

/ i !

.·

I I I ':: ~ I I

r,~~:

Ill MODERArE NUMBERS ~ RARE

CHECKLIST OF SPECIES

Exi l ia d i ckPJL~m.i Weaver

Gl vc~rus §£.·

~lyLilus §l.·

~C'.•ti::;

~trmiana (~..C'flvcr)

Ost.re.a id~·ie1L.:..;'.~; ---(.l~

Ost.rea grisieH .. si.s? (Effinger)

Pitnr. cali_fomiar:.:::t (Conrad)

Poli:1ices ~·

Pol inice.-; £2•

Polinices nuci:ormis (Gahb)

Spicula bioculptata (t'rulcrson & ltnna)

Sp:isula p?Ckanl i Dickernrn

TelliJ€ CC.l\ditze.Ib-iS

~~ver)

Turricu1a cc.Y..rl itz.erL<.;is (\Yeaver)

\'0Lsell2 ~·

BRACHIOPODA

Terebratal1a sn. ;\

Terebrata1 ia s 1 1. B

F/017

Sun.sat C•mp section

"' "' "' "' I "' I "' 1B g ~

Rock CrHI< section

"'l"'l"'l"'l"'I"' ~ ~ ~ t ~ ~

Nehalem NCI Jon

""' tool ~ N N ...., "'l "' I "' I "' I "' I "' I "' I "' ~i:;i::g:g:~g:

I 111111111111111111111

II At!UNDANT It ltlOOERATE NUMBERS ~ RARE

(plates 1, 2), which yielded the greatest number of

mollusks. The Sunset Camp section also yielded gastro­

pods, decapods, scaphopods and pelecypods.

63

Another notable collection site was that of the S & P

Railroad cut. Here several species of terrestrial plant

species were discovered in great profusion in tuffaceous,

calcareous light tan siltstone which probably represents a

tuff bed within the uppermost Tillamook Volcanics.

CHAPTER IV

PALEO ECOLOGY

Introduction

The climate of western Oregon during the late

Eocene was subtropical with a probable mean annual

temperature of 68° F (Chaney, 1933). This is based

largely on a diag-nostic subtropical flora which is

restricted to the sub-tropics of the western Hemisphere

(Detling, 1968). This flora reflected a warming trend

throughout the Eocene epoch. Benthonic foraminiferal

species assemblages in the measured sections of this

report do not directly indicate this warm environment,

however, because the number of species represented is

relatively small while numbers of individuals are often

high. This indicated a cool or temperate environment.

However, bottom temperatures were probably a function

of depth in a stratified Eocene sea, rather than of surface

conditions.

In this report diagnostic species in faunal assem­

blages have been used to determine features of the envi­

ronment of deposition. These features, although poten­

tially numerous, will be limited here to water depth,

temperature, and to a lesser extent, circulation. Refer-

ences used extensively in these interpretations were

Smith (1964), and Bandy and Arnal (1960).

Plectofrondicularia - Lenticulina Faunule

The lower faunule recognizable in the Cowlitz

Formation of the study area is found in the Nehalem

River Section and the lowermost portions of the Rock

Creek and Sunset Camp Sections of this report. This

f aunule encompasses the entire range of Cyclarnmina

65

pacif ica Beck in the several measured sections of this

report. This faunule also includes most of the local range

(teilzone) of Gyroidina condoni (Cushman & Scenck).

The presence of Cyclammina pacif ica Beck as well as

other forms in this faunule is indicative of deep water.

Cyclammina favors bathyal depths and cold temperatures

(Delise (1967, p. 15). Gyroidina condoni, (Cushman and

Schenck) likewise favors bathyal, cold water. Even more

telling is the abundance, in every sample, of Plecto­

frondicularia packardi Cushman and Schenck. Plecto­

frondicularia is restricted exclusively to bathyal depths

and cold waters.

Several other species of microfossils which are less

definitive with regard to depth also occur in this faunule.

The lagenids Lenticulina inornatus (d'Orbigny), L. welchi

Church, and L. texanus (Cushman and Applin) occur

regularly, especially toward the top of the unit. The

66

occurrence of these forms suggests that deposition

occurred no lower than upper bathyal depths.

Cibides - Lenticulina Faunule

The Cibides Lenticulina faunule described here

represents an outer neritic environment of deposition.

The abundant presence of Plectofrondicularia packardi

Cushman argues for deep water. Gyroidina species,

however, drop out in this faunule, only to reappear in

the basal Keasey Formation. Quinqueloculina sp. become

increasingly present in this faunule, indicating a pos-

sible shallowing trend. Cibides species, most notably c.

natlandi Beck, become increasingly abundant in this

faunule. The abrupt upper limit to the range of c. nat-

landi Beck probably marks the uppermost limit of the

faunule.

Many species of this faunule indicate cold water.

Pseudonodosaria ovata, Cushman and Applin, as well as P.

conica (Neugboren) are strong indicators of cold water.

Bathysiphon eocenica Cushman and G. P. Hanna, as well as

Globocassidulina globosa (Hantken) also indicate cold

bottom temperatures. The presence of the warm water

genus Quinqueloculina probably indicates a stratified

condition; near surface waters were significantly warmer

than those below a well defined thermocline. Quin-

queloculina individuals died and worked their way

downslope to mix with cold water forms (thanato­

coenosis).

Salinities were normal in this faunule.

Environment of Deposition of the Upper Cowlitz Sands

67

A fairly wide variety of opinion exists among recent

workers concerning the environment of deposition of the

Cowlitz Formation in Oregon. Bruer (1980) postulated a

bathyal "deep channel" model for the Cowlitz Formation

upper sands. Myers (1984) speculated that these sands

were deposited at outer neritic depths beyond a short

shelf and delta. In the Myers model, delta sands were fed

by gravity flow down the delta face and basin slope into

deep water. Jackson (1983), Timmons (1981), and many

others shared the view that the upper Cowlitz sands were

deposited in a wave-dominated inner neritic to beach

environment. Alger (1984) suggested that the Cowlitz

sands were deltaic.

What lines of evidence support these various models?

What, if anything, can be concluded from a discussion of

them?

Wesley Bruer in cooperation with Richhold Energy Co.

is credited with the discovery of the Mist gas field a few

miles north of the study area. He speculated that the gas­

bearing upper Cowlitz sands were deposited at bathyal

68

depths by strong traction currents. Figure 18, the "deep

channel model" roughly illustrates his concept.

Bruer noted that foraminiferal assemblages found

stratigraphically immediately above and below the upper

sands were representative of upper bathyal to outer

neritic depths. He also noted that wells drilled to the west

of the Mist field showed an abrupt loss of clean sands

along a line approximating the Clatsop County - Washing-

ton County boundary. In wells drilled immediately to the

East of Mist, the clean sands were replaced by coal depo­

sits and mudstones containing distinctly inner neritic

foraminiferal assemblages. These lines of evidence led

him to conclude that the thick sands from which the Mist

field produced were deposited in a well-defined, steep­

sided, deep channel analogous to the modern Straits of

Juan de Fuca. Bruer noted that traction loads on the

bottom of the Straits can include even coarse gravels, as

well as well sorted sand deposits.

Data from wells to the south of Mist in the Willamette

Valley showed that relatively clean arkosic sand deposits

included in the Cowlitz Formation and its southerly

equivalent, the Spencer Formation, showed a gradual east­

west widening and an apparently directly related reduc-

tion in porosity, and a thinning of the deposit. This Bruer

interpreted to be a widening of the channel which he had

postulated. In this broader channel, bottom currents

.. _

1300W 3:::>Vd V.L1'3:0

111"()1~

69 1300W 13NNVH:::> d330

71

lacked the high velocities and consequently strong sorting

ability of bottom currents in the narrower deeper channel

at Mist.

Jackson (1983), Timmons (1981), Van Atta (1971)

and many others have asserted that the clean upper sands

of the Cowlitz Formation were deposited in a shallow,

wave-dominated near-shore to beach environment, (fig.

19). This model is basically that of a ramp; deep-water

mudstones give way to a heterolithic zone at intermediate

depths, and sandstones replace these at shallower depths

approaching a beach.

Jackson (1983, p. 87) noted the presence of

hummocky cross stratification in the upper Cowlitz sand

deposits.

deposit.

He interpreted this to indicate a storm-wave

He cited sheet sand deposits on the modern

northern California coast as an analogue. Jackson also

indicated that he found shell layers, wood fragments, and

mudclasts at the bases of Cowlitz sand layers, as well as

ripples and other features as in the Northern California

deposits of shallow depth.

In addition, both Jackson and Timmons found certain

megafossils and trace fossils to reinforce their shallow

water interpretations. These include the trace fossils

Rosselia - Cylindrichus and ? Thalassinoides in Cowlitz

mudstones as well as the megafossil Brisaster.

N

,...

s

0 km

5

0

Q

m I

5Q

F/G

.21 -E

arly E

ocene Ty

ce-Flo

urn

oy

model fo

r shl"lf 'and

,ton

cs in a line \OU

fl't' ca,catlin:,: inlo dl·rp water to form

sand-rich fan

deposih. (a

fter M

.A. C

han

and

R.H

. Do

tt, Jr.)

73

Jack Myers, geologist for Oregon Natural Gas Develop­

ment Corp. (personal communication, 1984) advocated a

"deep sea fan model" for the upper Cowlitz sands. He

suggested that river-sorted sand was fed from a short

shallow shelf and delta system down into deeper water.

Myers noted similarities between electric log configu­

rations from wells in the Mist Field sands with known

subsea fans. He also pointed to the fact that arkosic sands

of the Cowlitz are locally juxtaposed against Tillamook

Volcanics rocks.

Myers adopted the model proposed by Chan and Dott

(1983) and shown below in fig. 21. Although the Chan

and Dott model referred to the early Eocene Tyee &

Flournoy Formations, Myers feels that the mechanisms

were probably similar. He also notes that a deeper water

interpretation is in conformity with the deep water

interpretation (based on paleontological evidence) for

much of the Cowlitz Formation siltstones both above and

below the upper Cowlitz sands.

Armentrout (personal communication Jan., 1984)

and others have advocated a "delta face model" for the

upper Cowlitz sands (fig. 20). This interpretation rests on

several facts: abundant plant material is found in the

Cowlitz, its proximity to coal fields near Chehalis

Washington, and a very thick (to 20,000 ft)' accumulation

within a depocenter immediately to the east, in the

74

Willamette Valley. These lines of evidence suggest a

nearby delta prograding westward during upper Eocene

time.

Discussion - The inner neritic model ignores the fact

that the microfossil assemblages found in the sediments of

the Cowlitz Formation in Oregon are clearly outer neritic

or more probably bathyal. Also, if the sands of the Cowlitz

Formation were deposited very near shore, then why has

no beach deposit ever been discovered nearby? Also the

presence of abundant mica tends to refute the near-shore,

wave-dominated, oscillatory motion included in the inner

neritic model.

The "Deep Channel" model uses the Straits of Juan de

Fuca as its modern analogue. Bruer cites the coarse sand

and gravel on the bottom of the Straights as evidence of

traction load movement of sediments a fair distance from

its source. The problem here lies in the fact that Pleisto-

cene glaciers lay in an area which is now occupied by the

Straits, leaving coarse morainal material upon the glaciers

retreat.

The submarine fan model calls for grainflow as a

mechanism for the deposition of sand, yet does not

adequately explain the presence of abundant crossbed-

ding, alternating paleocurrent direction, and hummocky

cross bedding of the upper Cowlitz sands. These sedimen-

75

tary structures indicate a high energy environment with

relatively strong currents.

This author suggests an "upper bathyal model" for

the upper Cowlitz sand which is in conformity with the

water depth determination of outer neritic depths, or

bathal depths, (fig. 22, 23). This model utilizes the

grainflow delivery mechanisms of the submarine fan

model of Chan and Dott (1983) and Myers (1984) but also

calls for the strong traction currents of Bruer's model to

account for the alternating direction of cross bedding and

sheet sand nature of the formation. In this model these

energetic bottom currents distribute sand north and south

of a fan center near Mist. This center is found seaward of

a delta perched on a short shelf immediately to the east of

the Mist area. River-winnowed sand cascades down the

face of this delta and is distributed there in a fan.

This model accounts for the abundance of vitrinite in

the upper Cowlitz sands by allowing for close proximity

to the Cowlitz Delta. It does not demand sudden eustatic

changes in sealevel; all deposition takes place in outer

neritic to upper bathyal depths as indicated by fora-

miniferal assemblages. The deposition of finer-grained

material prior to the deposition of sand is explained by

the growth of the Cowlitz Delta on the shallow shelf. Sand

accumulates on the delta until it reaches the shelf margin.

9L

77

At that time large amounts of clean sands would begin to

cascade over the margin into deeper water.

This author proposes that the environment of

deposition of the Cowlitz Formation in Oregon was some­

what deeper than the inner neritic to middle neritic

interpretation of Jackson, Van Atta, and Timmons and

others who have also discussed the environment of

deposition of the Cowlitz Formation in the Upper Nehalem

River Basin. This author basically subscribes to the

transgressive - regressive history of the formation as

described by McKeel (1983, p. 3) and largely agrees with

McKeels water depth determinations.

The wide variety of opinion concerning the environ­

ment of deposition of the Cowlitz Formation as well as

inferred mechanisms of sediment transport appear to

leave the door open to speculation. The model which is

presented here is an attempt to bring together various

lines of evidence. In doing so, the information generated

by foraminiferal indicators of water depth, temperature

and circulation were given greater weight than that

generated from the interpretation of sedimentary

structures or trace fossils.

SL

f:Z-Dl:J

auoispnw JBMO/

~ ,... ,... loo ~ 0 0-

"' ~ ,... ~ :i: 0

C')

0 ~

~ ------t-

pues uKJdn

-t N

-------auoispnw Jaddn

~ 0 3 5 c:

~ ::J

Cl> i ID ... ... ...

::J ::J O" Cl>

" Ill

::!. ::J ~. s ID g: '<: ~· ~. !. g-.

79

CHAPTER V

AGE AND CORRELATION

Local Biostratigraphy

The Cowlitz Formation was deposited during the

Narizian Foraminiferal Stage of Mallory and the Bulimina

schencki - Plectofrondicularia Cf P. jenkinsi Zone of Rau is

the only zone recognized. The lower portion of this zone

is represented by the Plectofrondicularia - Lenticulina

faunule, comprising all of the Nehalem River Section, the

lowermost portion of the Rock Creek Section, including

sample sites PSUA250 - PSUA252, and the base of the

Sunset Camp Section, including sample site PSUA259.

The intermediate portion of the composite section of

this report is included in the Cibicides - Lenticulina

faunule. This extends from sample site PSUA247 to PSUA

249 in the Rock Creek Section. In the Sunset Camp Section

this faunule is present in sample sites PSUA260 through

PSUA266.

The uppermost faunule occurs in a single sampling

site, PSUA267, assigned to the lowermost Keasey Forma­

tion, as well as the lower Refugian Stage of Rau. It is

herein called the Ceratobulimina - Vaginulinopsis faunule.

80

The stratigraphic occurrence of these faunules is shown in

the correlation of sections, (fig. 16).

The Narizian-Refugian Stage Boundary

The Cowlitz-Keasey contact is often gradational

(Warren and Norbisrath, 1946}, or at least difficult to

pinpoint in the field. Likewise, the location of the

Narizian - Refugian stage boundary with which it is

sometimes coincident is often problematic, particularly in

this section because the sediments which bracket the

boundary and the contact are largely barren.

McKeel (1938} used the occurrence of Cibicides

natlandi Beck to delimit the Narizian zone in the upper

Nehalem River Basin in his micropaleontological analysis

of drill cuttings from gas wells in the area. He also found

that the rare occurrence of the planktonic form Pseudo­

hastigerina micra (Cole} could be used to indicat~ a

position just below the stage boundary. In the Sunset

Camp section C. natlandi occurs commonly up to and

including the assemblage collected at locality PSUA266

but not above. P. micra makes its only appearance at this

same locality. Therefore, the stage boundary probably

occurs stratigraphically above this point.

The assemblage isolated from locality PSUA

267 contains many Refugian forms included in the

Sigmorphina Schencki Zone species list of Rau (1981},

81

including the first occurrences of the forms Vaginulinopsis

saund~r~i (Hanna and Hanna) and Marginulina alazanensis

Nuttall. Samples taken approximately 25 meters strati­

graphically above locality PSUA267 include such

diagnostically lower Refugian forms as Melonis halkyardi

(Cushman) and Pseudoglandulina inflata (Bornmann).

Forty meters stratigraphically below locality PSUA

267, nearly barren sediments display a sudden loss of

mica, which was characteristically so abundant in all

Cowlitz Formation sediments. This lithological contrast

marks the Cowlitz-Keasey contact as defined by Van Atta

(oral comm. 1985). For convenience, the stage boundary

is herein assigned to this contact because it is bracketed

by rocks containing assemblages which are representative

of the Refugian Stage above and the Narizian Stage below.

Correlation

Based on the assemblages found in samples taken

from the measured sections of this study, the Cowlitz

Formation can be correlated with the Type Cowlitz

Formation in Washington, the Spencer, Yamhill, Nestucca,

and Coaledo Formations of Oregon, the Mcintosh

Formation of Washington and the Tejon Formation of

California.

82

SYSTEMATIC CATALOGUE

In the following synonomies, identifications are

based primarily on published figures and descriptions.

Special note has been made of species which have been

compared with type material on deposit in the Earth

Sciences Museum at Portland State University. The

systematic arrangement of the foraminifera follows that

of Cushman (1950).

Phylum PROTOZOA

Class SARCODINA Butschli, 1881

Order FORAMINIFERA d'Orbigny, 1826

Family RHIZAMMINIDAE

Genus Bathysiphon M. Sars 1872

Bathysipb_on eocenicus Cushman and G.D. Hanna

~athysiphon eocenica Cushman and G.D. Hanna, Cushman and McMasters 1936, p. 508, pl. 74 fig. 1 Weaver and Molander, 1964, p. 176, pl. 1 fig. 2; Gaston 1972 p. 46, [hypotype examined] •

Bathysiphon eocenicus Cushman and G. P. Hanna, Mallory, 1959 p. 105, pl. 1 fig. 4; Callendar, 1977 p. 88 [hypotype examined], McDougall, 1980, p. 23 fig. 1

Hypotype no. 00517 loc. PSUA 251

Family MILIOLIDAE

Genus Quinqueloculina

Quinquel()_C_ulin~ imperialis Hanna and Hanna

Quinqueloculin~ i~p~~ialis Hanna and Hanna, Beck 1943, p. 592, pl. 98 figs. 9, 10; Rau, 1948, p. 159, pl. 27, figs. 12-14, Gaston, 1984 p. 51 [hypotype examined] Callendar, 1977, p. 90 [hypotype examined]

Hypotype no. 00518 loc. PSUA 251

Family AMMODISCIDAE

Genus Ammodiscus Reuss 1861

Ammodiscus coombsi Beck

Ammodiscus c~~~bsi Beck plate 98, fig. 1

Hypotype no. 00519 loc. PSUA 251

Family LITUOLIDAE

Genus Cycl~mmina H.B. Brady 1876

fy_~~3~rniila pac j._fJ_ca Beck

83

Cyclammin~ pacifica Beck, 1943, pl. 98 figs. 2, 3; Detling, 1946, p. 352, pl. 46, fig. l; Cushman and Stewart, 1947, p. 74 pl. 9, figs. 1, 2; Rau, 1948 p. 157, pl. 27, figs. 7, 8; Rau 1951, p. 429, pl. 63, fig. 18.

Hypotype no. 00520 loc. PSUA 249

Family LAGENIDAE

Genus Dentalina

Dentalina communis (d' Orbigny)

Dei:i!:~l_J:na commu~~§_ (d'Orbigny) Beck, 1943, p. 598, pl.105, fig. 22; Smith, 1957, p. 165, pl. 22, fig. 9; Mallory, 1959, p. 162, pl. 12, fig. 11; pl. 41, fig. 6; Gaston, 1974, p. 64 [hypotype examined]; Callendar 1977, p. 110 [hypotype examined]

Hypotype no. 00521 loc. PSUA 258

Dentalina dusenburyi

Hypotype no. 00522 loc. PSUA 262

De_ntaliQ~ sp

Hypotype no. 00523 loc. PSUA 258

Genus Lag~_!:l-~

Lagena sp.

Hypotype no. 00524 loc. PSUA 267

Genus Lenticulina

Lenticu~in~ inornata (d'Orbigny)

84

Lenticulina inornata (d'Orbigny) Tipton, Kleinpell, and Weaver, 1973 p. 45, pl. 2, fig. 9a, b; McDougall 1980, p. 41, pl. 7 figs. 11, 12.

Robulus inornatus (d'Orbigny) Beck, 1943, p. 595 pl. 104, figs. 1 - 4; Mallory, 1959, p. 137, pl. 7, fig. 15a, b; pl. 40, fig. Sa, b; Callendar, 1977, p. 97 [hypotype examined]

[?] Robulus inornatus (d'Orbigny) Gaston, 1974, p. 55 [hypotype examined].

Hypotype no. 00525 loc. PSUA 249

Lenticulina texanus (Cushman and Applin)

Len~~~1:!l_in_~ te~~p~s (Cushman and Applin) McDougall, 1980, p. 41, pl. 7, figs. 14, 15.

Robulus texanus (Cushman and Applin) Beck 1943, p.

85

603, pl. 103, fig. 1 - 5; Rau, 1948, p. 164, pl. 29, fig. 16, 17.

Hypotype no. 00526 loc. PSUA 248

Lenticulina welchi (Church)

Lenticulina welchi (Church) McDougall, 1980, pl. 8, fig. 1 - 4.

Robulus we~chi (Church) Beck, 1943, p. 596, pl. 102, fig. 4, 8; Detling, 1946, p. 353, pl. 48, fig. 2a, b; Rau, 1948, p. 161, pl. 28, fig. 16, 17; Mallory, 1959, p. 143, pl. 7, fig. 8a, b; Gaston, 1974, p. 58, (hypotype examined) Thoms, 1975, pl. 2, fig. la, b; Callendar, 1977, p. 102 (hypotype examined)

Hypotype no. 00527 loc. PSUA 255

Lenticulina sp.

Hypotype no. 00528 loc. PSUA 255

Genus M~~g___i_J_:!_uli_n_~ d'Orbigny, 1826

Marginulina sp.

Hypotype no. 00529 loc. PSUA 267

One incomplete specimen collected from the upper

Sunset Camp Section exhibits the tight coiling of early

chambers and uniserial arrangement of final chambers

characteristic of this genus. The specimen resembles M.

alazanensis.

Genus Nodosaria Lamarck 1812

Nodosaria sp. a

Hypotype no. 00530 loc. PSUA 255

Single fragment in the Rock Creek Section was insuf-

ficient to further identify this specimen.

Genus Pse~_d_?g_!-9~_9_\.l~-L~-~ Cushman 19 29

Ps~\.lcj()Q l_a]'1Q\.l)-_! na ova ta Cushman and Applin

Pseud_og!~__ri._c]_\.lJ__i._1'1~ ova ta Cushman and Appl in, Mallory 1959, p. 174, pl. 28, fig. 9a, b; Gaston 1974, p. 70 [hypotype examined] Callendar 1977, p. 123 [hypotype examined] •

Hypotype no. 00531 loc. PSUA 251

Genus Saracenaria De France

Saracenaria hantkeni Cushman

Saracenaria h~nt_kei::!t Cushman, Beck, 1943, p. 606, pl. 106, fig. 9, 12; Mallory p. 153, pl. 27, fig. 19, a, b; McDougall, 1980, p. 42, pl. 9 fig. 12 -17.

Hypotype no. 00532 loc. PSUA 261

Genus Vaginulinopsis

Vaginulinopsis sau~~ersi (Hanna and Hanna)

Vaginulinopsis saundersi (Hanna and Hanna) Beck, 1943,

86

p. 598, pl. 105, figs. 1, 2, 4, 5, 10; Rau, 1948, p. 165, pl. 30, fig. 20-23; Mallory, 1959, p. 157, pl. 11, fig. lOa, b; Gaston, 1974, p. 63, (hypotype examined); Callendar, 1977 p. 108, (hypotype examined); McDougall, 1980, p. 42, pl. 10, figs. 8, 9.

87

Hypotype no. 00533 loc. PSUA 267

Genus Vaginulina

Vaginulina_ sp.

Hypotype no. 00534 loc. PSUA 258

Family POLYMORPHINIDAE

Genus Globulina d'Orbigny 1839

Globulina landesi (Hanna and Hanna)

Globu_liQ~ la!}g~si (Hanna and Hanna), Beck 1943, p. 603, plate 106, figs. 14, 16, Mallory 1959, p. 178, pl. 36, figs. 13a, b.

Polymorphina !__~Q~esi Hanna and Hanna, 1924, p. 60, pl. 13, figs. 16, 17.

Hypotype no. 00535 loc. PSUA 261

Genus Guttulina d'Orbigny 1839

G~ttulina irr~9~la!i~ (d'Orbigny)

Guttulina irregulari_a_ (d'Orbigny) Cushman 1935, p. 24, pl. 9, figs. 13 - 16; Beck 1943, p. 602, pl. 106, figs. 3 -5; Mallory 1959, p. 177, pl. 14, fig. 13a, b; Gaston 1974, p. 72 (hypotype examined); Callendar, 1977, p. 127 (hypotype examined).

Hypotype no. 00536 loc. PSUA 262

Genus Pseudogl~p_du~JnA

f§~Ud_ogla_~c!1:!).J._.!1a ~onj.ca_ ( Neugeboren)

88

conica (Neugeboren) Beck 1943, p. 605, ~~~udog~and u_! J:na pl. 105, fig. 12; 36, fig. lla b.

Mallory 1959, p. 173, pl. 33, fig. 4, pl.

Pseudonodosaria conica (Neugeboren) McDougall 1980, p. 43, pl. 9, fig. 7, 8.

Hypotype no. 00537 loc. PSUA 259

Family HETEROHELICIDAE

Genus Plectofrondicularia Liebus, 1903 -------------·-

Pl~ct~frondicuJ_~ria pack~~di Cushman and Schenck

Plectofrondicu_l_a_~~9 pac:;)<ardi Cushman and Schenck, Detling 1946, p. 355, pl. 49, fig. l; Mallory, 1959, p. , pl. fig. , Callendar 1977, p. 134 [hypotype examined]; Mc Doug a 11 , 1 9 8 0 , p • 4 2 , p 1. 11 , f i gs • 1 , 2 •

Plectofro~~i~~l_arj~ packa~di multiline_~ta Cushman and Simonson, Rau, 1948, p. 165, pl. 30, fig. 19.

Hypotype no. 00538 loc. PSUA 249

Family BULIMINIDAE

Genus Boljy_ina d'Orbigny, 1839

Bolivina basisenta Cushman and Stone

~olivina basi~enta Cushman and Stone, Gaston 1974, p. 80 [hypotype examined] Callendar 1977, p. 151 [hypotype examined]

Hypotype no. 00539 loc. PSUA 258

Bolivina Klienpelli Beck

Bolivina kl~inpell_i Beck, 1943, p. 606, pl. 107, fig. 39; Mallory, 1959, p. 201, pl. 16, fig. 20; Gaston, 1974, p. 81

[hypotype examined]; Callendar, 1977, p. 152 [hypotype examined]; McDougall, 1980, pl. 14, figs. 5, 6.

Hypotype no. 00540 loc. PSUA 2

Genus Bulimina

Bulimina schencki Beck

Bulimina schencki Beck

Hypotype no. 00541 loc. PSUA 255

Bulimina sp.

Hypotype no. 00542 loc. PSUA 250

One poorly preserved specimen from the Rock Creek

Section seems best referred to this genus.

Genus Globobulimina Cushman 1927

G!~pQpuli!l!_ina pacif_i~~ Cushman

Glob~b~!i~i0a pa~jJ_L~~ Cushman, Mallory, 1959, pl. 16, fig. 17; Gaston, 1974, p. 79 (hypotype examined); Callendar, 1977, p. 148 (hypotype examined).

-~:g_<2.!?_o_q~li_Tl!_ina cf. G. I?_C1cJfic_§ Cushman, Rau, 1948, p.

89

171, pl. 30, fig. 5; Weaver and Weaver, 1962, p. 32, pl. 9, fig. 16.

Hypotype no. 00543 loc. PSUA 252

Globobulimina sp.

Hypotype no. 00544 loc. PSUA 252

90

One poorly preserved specimen from the Rock Creek

Section seems best referred to this genus.

Genus Trifarina Cushman 1923

Trifarina hanni Beck

Trifarina hanni Beck, McDougall, 1980, p. 37, pl. ' fig.

Angulogerj_!!~ h~~~i Beck, 1943, p. 607 - 608, pl. 108, figs. 26, 28.

Hypotype no. 00545 loc. PSUA 261

Family ROTALIIDAE

Genus Gyroi_dina D'Orbigny, 1826

Gyroidina condo~i_ (Cushman and Schenck)

Gyroi_d in~ C~!]_Q_sm i (Cushman and Schenck) , Tipton, Klienpell, and Weaver, 1973, p. 60, pl. 9, fig. la - c; Gaston, 1974, p. 85 (hypotype examined); Thoms, 1975, pl. 3, fig. 6 a - c; Callendar, 1977, p. 161 (hypotype examined); McDougall, 1980, p. 46, pl. 27, fig. 5.

Hypotype no. 00546 loc. PSUA 249

Gyro id ina o~i~~l<i_!'."i_s d 'Orbigny var. pla!lata Cushman

Gyr~idi~~ o~~i~ularj~ d'Orbigny var. planata, Cushman, Weaver and Weaver, 1962, p. 36, pl. 13, fig. la - c.

Gyroidina orbiculari~ planata Cushman, Rau, 1948, p. 171, pl. 31, fig. 12 - 14; Gaston, 1974, p. 86, (hypotype examined); Thoms, 1975, pl. 2, fig. 18 a - c; Callendar, 1977, p. 162 (hypotype examined); McDougall, 1980, p. 46, pl. 27, figs. 7 - 9.

Hypotype no. 00547 loc. PSUA 267

91

Family CASSIDULINIDAE

Genus Ceratobulirnina Toula 1915

Ceratobulirnina washburnei Cushman and Schenck

Ce:i;?tobul irnina ~~§!:i!=>l1:t;n~_i Cushman and Schenck, Beck, 1943, pl. 108, figs. 20, 24; Rau, 1948, pl. 31, figs. 15 -17; McDougall, 1980, pl. 29, figs. 10, 11.

Hypotype no. 00548 loc. PSUA 267

Genus ~2<?!?-_i_q~§ Montfort, 1808

Epsrnic1e§ ~ex_i_cana (Cushman)

§.!2<2!1_id~§ !!l_~~icana (Cushman), Mallory, 1959, p. 237, pl. 37, fig. 11; Weaver and Weaver, 1962, p. 37, pl. 13, fig. 4a - c; Gaston, 1974, p. 86, (hypotype examined); Thorns, 1975, pl. 3, fig. 3a - c; Callendar, 1977. p. 165 (hypotype examined); McDougall, 1980, p. 45, pl. 23, figs. 7 - 9.

Epgnid_E!!3 y_~g~_a~nsj_§ Weinzierl and Applin, Beck, 1943, p. 608, pl. 108, figs. 1, 4.

Hypotype no. 00549 loc. PSUA 251

Genus Globoc_§_§!3~_duJ_i_I!~ d 'Orbigny, 1826

Glob_oc_C!S!3 idul ina glQ_!?Q_S_~ (Hant ken)

Cassiq_l:l~in_a g_~<_?Q<_?_S_cl Hantken, Beck, 1943, p. 611, pl. 108, figs. 7, 13, 14; Detling, 1946, p. 358, pl. 51, fig. 3a, b; Mallory, 1959, p. 226, pl. 33, fig. lla, b; Weaver and Weaver, 1962, p. 38, pl. 16, fig. 3a - c; Gaston, 1974, p. 89 (hypotype examined); Callendar, 1977, p. 171 (hypotype examined).

9_:!_9boc:assidulJna 9!<:>1?013§_ (Hantken), Smith, 1971, p. 63, pl. 9, fig. 6a, b.

92

Hypotype no. 00550 loc. PSUA 251

Family CHILOSTOMELLIDAE

Genus Allornorphj_11a Reuss 1850

A!!~~~~phin~ IDC'l~~~~~?~A Karrer

Allolfl_o_r:Pl"linC'l rnac_:t;?§_torn9 Karrer, Beck, 1943, pl. 108, figs. 7, 13, 14; Rau, 1948, pl. 31, figs. 4, 5; Gaston, 1974, p. 90 (hypotype examined); Callendar, 1977, p. 172 (hypotype examined).

Hypotype no. 00551 loc. PSUA 250

Family HANTKENINIDAE

Genus E_§eudohastigerin_C'l Banner and Blow, 1959

E_§_~~_Q_~hastige!'."ina rnicra (Cole)

!i~QiQT! IIl_iS::t;urn Cole, Mallory, 1959, p. 181, pl. 15, figs. 3a - c; Thorns, 1975, pl. 4, fig. 3a, b.

Ps~~_<!_Q_hastigerinC1 rnicra (Cole) Gaston, 1974, p. 91, (hypotype examined); Callendar, 1977, p. 174 (hypotype examined) •

Hypotype no. 0052 loc. PSUA 267

Family ANOMALINIDAE

Genus ~iQ~cides Montford, 1808

~!~j~ides baileyi Beck

Cibicides baileyi Beck, 1943, pl. 109, figs. 7 - 9.

Hypotype no. 00553 loc. PSUA 250

Cibicide? ~oqgei Cushman and Schenk

Boldi~ hodg~i (Cushman and Schenck), McDougall, 1980, pl. 29, figs. 4 - 6.

93

fibid~s h9dgei Cushman and Schenck, Beck 1943, pl. 109, fig. 24 - 28; Mallory, 1959, p. 265, pl. 24, figs. 6a - c; Hornaday, 1961, pl. 13, fig. la - c; Callendar, 1977, p. 181 (hypotype examined).

Hypotype no. loc. PSUA 255

Cibides natlandi Beck

f!):)_icides natlandi Beck, 1943, pl. 109, figs. 1, 5, 13; McDougall, 1980, pl. 24, figs. 7 - 9.

Hypotype no. 00555 loc. PSUA 260

Cibicides p.

Hypotype no. 00556 loc. PSUA 261

One poorly preserved specimen from the Sunset Camp

Section was referred to this genus.

94

DESCRIPTIONS OF LOCALITIES

All of the following localities are found in the eastern

Nehalem River Valley in an area approximately described

by a triangle with points at Keasey, Cochran and Timber,

Oregon. This includes western parts of Columbia and

Washington Counties and to a very limited extent the

easternmost portion of Tillamook County. The United

States Geological Survey Map of the Timber Quadrangle

(15 minute series, scale 1:62500, 1955) and the United

States Geological Survey Map of the Clear Creek

Quadranqle (15 minute series, scale 1:62500, 1955) were

used here. Locality numbers refer to the collections of the

Earth Sciences Museum of Portland State University,

Portland, Oreqon. Localities are listed below as they

appear in their respective measured sections.

Nehalem River Section - --

Representing the lowermost portion of the Cowlitz

Formation and including its contact with the Tillamook

Volcanics Series, this section was measured along the

upper Nehalem River west of Timber, Oregon. The

Nehalem River flows southeast here (fig. 5) along a fairly

straight line which may be fault controlled.

The beginning and lowermost point stratigraphically,

of the traverse occurs in the NW 1/4, NW 1/4, SW 1/4 of

Section 30, T3N, R5W. This point is marked by a smooth,

95 black, massive basalt outcropping in the riverbank which

is the last basalt flow recognizable in moving downstream

(upsection) and is recognized in this report as the lower

contact of the Cowlitz Formation. The final point on the

traverse, also in the Nehalem River, is at locality PSUA

258 (fig. 5). At this point the course of the river swings to

the northeast where it approximates strike. This point is

located in the SE 1/4, NE 1/4, NE 1/4, Section 31, T3N,

R5W. The section as a whole begins in basaltic

conglomerate, and ends in mudstone. All foraminiferal

samples were taken from the bottom and banks of the

Nehalem River.

Locality PSUA 253

Located on the north bank of the Nehalem River, 22.3

meters stratigraphically above the base of the Nehalem

River Section as described above. The rock here is a fine

grained, greenish-gray tuffaceous siltstone.

Locality PSUA 254

Located on the south bank of the Nehalem River,

103.2 meters stratigraphically above the base of the

section in well-bedded, medium-gray, soft mudstone.

Locality PSUA 255

Located on the bottom of the Nehalem River 117.l

meters stratigraphically above the base of the section in

medium-gray, "greasy" claystone.

Locality PSUA 256

Located on the bottom of the Nehalem River 161.7

meters stratigraphically above the base of the section in

light-gray, well-bedded mudstone.

Locality PSUA 257

Located on the bottom of the Nehalem River 206.4

meters stratigraphically above the base of the section in

medium-gray, poorly bedded to massive, bioturbated,

micaceous siltstone.

Locality PSUA 258

Located on the bottom of the Nehalem River 253.5

meters stratigraphically above the base of the section in

medium-gray massive, micaceous siltstone.

Rock Creek Section

This section was measured along the bed of Rock

Creek (fig. 8) from a ruined railroad trestle upstream of

the former townsite of Keasey to a point immediately west

of the town. Cowlitz Formation rocks are faulted against

Tillamook Volcanics rocks at a point several hundred

96

97 yards below the ruined railroad trestle, therefore all

collections were made downstream of this contact to the

termination of the traverse imme-diately west of Keasey.

The quarter section descriptions of these three points are:

trestle; SE 1/4, NW 1/4, SW 1/4, Sec. 5, T4N, R5W, contact;

NE 1/4, NW 1/4, SW 1/4, Sec. 5, T4N, R5W, Keasey; NW

1/4, SE 1/4, NW 1/4, Sec. 5, T4N, R5W.

Locality PSUA 252

Located in the east bank of Rock Creek 6.3 meters

stratigraphically above the base of the section west of

Keasey in calcareous light gray mudstone.

Locality PSUA 251

Located in the bottom of Rock Creek 18.4 meters

stratigraphically above the section base in laminar,

bedded, lignite-rich dark-gray, siltstone.

Locality PSUA 250

Located in the bottom of Rock Creek 30.7 meters

stratigraphically above the base in medium gray, well

bedded mudstone.

Locality PSUA 249

Located in the bottom of Rock Creek 42.3 meters

stratigraphically above the base in light-gray, thin­

bedded, coarse siltstone.

Locality PSUA 248

Located in the north bank of Rock Creek 79.1 meters

stratigraphically above the base in light-gray, fine­

grained, sandy, planar, bedded siltstone.

Locality PSUA 247

Located in the bottom of Rock Creek 121.7 meters

stratigraphically above the base in medium-gray, massive

siltstone.

Sunset Camp Section

This long section follows the Nehalem River from the

Sunset Highway bridge at Timber Junction to a logging

company bridge approximately two kilometers upstream.

98

The base of the section occurs at the bridge at Timber

Junction. The uppermost portion of the section includes the

Cowlitz-Keasey contact as well as a few tens of meters of the

basal Keasey Formation. The quarter section coordinate for

the lower and upper bridges are respectively: SW 1/4, SW

1/4, NW 1/4, Sec. 10, T3N, R5W, and SW 1/4, SW 1/4, NE 1/4,

Sec. 15, T3N, R5W.

Locality PSUA 259

Located on the bottom of the Nehalem River 15.6

meters stratigraphically above the base in medium-gray,

well-bedded siltstone.

Locality PSUA 260

Located on the bottom of the Nehalem River 43.7

meters stratigraphically above the base in medium-gray,

soft, bioturbated mudstone.

Locality PSUA 261

Located on the bottom of the Nehalem River 68.7

meters stratigraphically above the base in medium-gray,

micaceous, bioturbated mudstone.

Locality PSUA 262

Located on the bottom of the Nehalem River 109.4

meters stratigraphically above the base in medium-gray,

micaceous, well-bedded siltstone.

Locality PSUA 263

Located on the eastern bank of the Nehalem river

168.7 meters stratigraphically above the base in dark

gray, micaceous, calcareous mudstone.

Locality PSUA 264

Located on the bottom of the Nehalem River 225.3

meters stratigraphically above the base in light gray,

micaceous siltstone.

99

Locality PSUA 265

Located on the western bank of the Nehalem River

262.5 meters stratiqraphically above the base in dark,

gray-green, lignitic, micaceous siltstone.

Locality PSUA 266

Located on the bottom of the Nehalem River 300.1

meters stratigraphically above the base in light gray,

calcareous, well indurated, sandy siltstone.

Locality PSUA 267

Located on the bottom of the Nehalem River 463.5

meters stratiqraphically above the base in medium-gray,

tuffaceous, fine grained, non-micaceous mudstone.

100

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